Table of Contents
- What mobile app development in London actually involves
- How much does mobile app development in London cost in 2026?
- How long does it take to build a mobile app?
- React Native, Flutter, or native: which mobile stack fits
- The tech calls a founder makes without a CTO
- What we learned building Ove, a London dating app
- The hidden complexity that quietly inflates a mobile app budget
- Submitting to the app stores: what actually happens
- How to brief a mobile app so the quote is real
- Frequently Asked Questions
- Conclusion: your mobile app development London decision in one move
Quick answer: Foundry 5 is a London studio where mobile app development in London means building production iOS and Android apps for startups and SMEs, usually React Native for one codebase across both stores. A focused first version typically runs 40,000 to 90,000 pounds and ships in 10 to 16 weeks. Scope moves that number, not the postcode.
You have three quotes open in three tabs. One says 25,000 pounds. One says 90,000. One says a quarter of a million. All three are for the same app you described in the same email. This is the first real lesson in mobile app development in London: the price is not a fact about the app, it is a fact about the specification behind it.
Founders feel that gap as noise. It is actually signal. A vague brief invites vague numbers, and vague numbers protect the agency, not you. A precise brief does the opposite: it forces every studio to quote the same scope, and the quotes start to converge.
This guide is written for the non-technical founder who has to make real engineering decisions without an engineer in the room. It covers what the work involves, what it costs in 2026, how long it takes, and the platform and architecture calls that decide both. The goal is not to make you a developer. The goal is to make you impossible to overcharge.
What mobile app development in London actually involves
Mobile app development in London is the work of turning an idea into a signed, tested, store-approved app that real people can install and use every day. Foundry 5 treats it as four connected jobs: the app your users touch, the backend that feeds it, the store presence that ships it, and the maintenance that keeps it alive after launch. Most founders only budget for the first.
The app itself is the visible part: screens, flows, gestures, offline states, push notifications. It is also the smallest part of the real cost. Behind every screen sits an API, a database, authentication, payments, and a dozen third-party services that each have their own failure modes.
Think of the app as the storefront and the backend as the warehouse. A beautiful storefront with an empty, disorganised warehouse sells nothing. The best mobile builds spend as much design effort on the warehouse as on the window, because that is where reliability, speed, and cost actually live.
So when a studio quotes you, ask what they included. A number that only covers the two platforms and skips the backend, the store submissions, and three months of post-launch support is not cheaper. It is incomplete.
How much does mobile app development in London cost in 2026?
Mobile app development in London in 2026 typically costs between 40,000 and 250,000 pounds, and Foundry 5 sees most funded first builds land between 40,000 and 90,000 pounds. London agencies price a working day at roughly 500 to 1,200 pounds per person, which puts the city 30 to 50 percent above the wider UK. The specification decides where in that range you sit, not the city on the invoice.
It helps to stop thinking in one number and start thinking in three bands. Each band buys a different kind of certainty.
| Band | Typical London range | What it buys |
| MVP | 40,000 to 90,000 pounds | One core workflow, one user type, iOS and Android, a lean backend. Proof, not polish. |
| Product | 90,000 to 160,000 pounds | Multiple user roles, payments, real design system, analytics, a few integrations. |
| Scale | 160,000 pounds and up | Heavy integrations, real-time features, compliance, and a team that maintains it. |
The single most expensive decision is not a feature. It is ambiguity. A build that starts before the scope is frozen pays for the same screen twice: once as the developer imagined it, once as you actually meant it. If you want the honest version of where the money goes, read our breakdown of the real cost of building a mobile app before you approve any quote.
Consider a founder who budgets 50,000 pounds, then adds a second user type, in-app payments, and a chat feature during the build. Each felt small in the meeting. Together they can double the number and add two months. Scope creep is not one big decision. It is twenty small ones nobody wrote down.
Want a real number instead of a range? If you can describe the one workflow that has to work, we can scope it into a fixed number in a single call. Book a free 30-minute discovery call with Foundry 5. No pitch deck, no obligation, just a direct read on what your app should cost.
How long does it take to build a mobile app?
Most mobile apps take three to six months to reach a confident launch. A focused MVP can ship in 10 to 16 weeks, while a multi-role product with payments and integrations runs six to nine months or longer. The biggest lever on the calendar is the same as the one on the budget: how much you freeze before development starts.
A realistic mobile timeline moves through four phases, and skipping the first is what breaks the last three.
The four phases, honestly
- Discovery and design, 2 to 4 weeks: turn the idea into flows, screens, and a frozen scope. The cheapest phase to change your mind in.
- Core build, 6 to 12 weeks: the app, the backend, and the integrations, shipped in working increments you can actually try.
- Testing and hardening, 2 to 4 weeks: real devices, edge cases, performance, and the store paperwork that trips up first-timers.
- Launch and iterate: submit, ship, watch real usage, and fix what the plan could not predict.
Adding people does not reliably buy speed. A famous pattern in software delivery is that late teams who add developers often get slower first, because the newcomers need context the deadline cannot spare. Protect the timeline at the front, in discovery, rather than trying to rescue it at the end with headcount.
React Native, Flutter, or native: which mobile stack fits
The framework question decides your budget, your hiring, and your speed, so founders ask it early and usually frame it wrong. It is rarely native versus React Native in the abstract. It is: what does this specific product need to do, and where is one codebase a saving rather than a compromise?
React Native lets one team ship both iOS and Android from a shared codebase, which is why it powers production apps at Meta, Microsoft, Discord, and Coinbase. Shopify builds all of its mobile apps with React Native and reports sharing roughly 80 percent of its code across the two platforms, which is time not spent building the same feature twice. For most startups, that shared codebase is the difference between launching on both stores at once and launching on one and hoping.
| Approach | Best when | The trade-off |
| React Native | You want both platforms fast, on one budget, with mostly standard UI. | Deep platform-specific tricks need native modules, so truly novel hardware work costs more. |
| Flutter | You want one codebase and a highly custom, animation-rich interface. | Smaller UK hiring pool than React Native, and a different language, Dart. |
| Native (Swift and Kotlin) | You lean hard on device hardware, top-tier performance, or platform-only features. | Two codebases, two teams, roughly two times the build and maintenance cost. |
The honest concession: native still wins for a narrow class of apps. If your product is a high-frame-rate game, a camera app doing real-time computer vision, or something that lives or dies on the newest OS feature, pay for native and do not flinch. For the other 80 percent of founder apps, one codebase is the smarter first move. Our fuller take on choosing between React Native, Flutter, or native walks through the decision product by product.
The tech calls a founder makes without a CTO
Without a technical co-founder, you will still own decisions that shape the product for years. You do not need to write the code. You do need to ask the right questions and recognise a weak answer. Making the right tech calls without a CTO comes down to four areas that quietly decide everything downstream.
The API is the product’s spine
Your app is only as good as the API feeding it. A clean, well-documented API means new features slot in; a messy one means every change is surgery. This is why designing a mobile app API deserves real thought before the first screen is built, not after. Ask any studio how they version the API and how the app behaves when the network drops. The answer reveals whether they build for the demo or for the field.
Own your code and your keys
Before anyone writes a line, settle who owns the repository, the Apple and Google developer accounts, and every third-party key. The studio should build in your accounts, not theirs. If a partner is vague about handover, that is not a paperwork detail. That is your product held hostage.
Plan for the intelligent features you will want
Most apps eventually want a smart layer: search that understands intent, a support assistant grounded in your own content, recommendations that improve with use. Building the app so it can later plug into a retrieval system is far cheaper than retrofitting one. If that is on your roadmap, our RAG and AI development work exists precisely so the intelligent version of your app is a phase two, not a rebuild.
What we learned building Ove, a London dating app
Guides list features. Studios that have shipped remember the parts that hurt. Foundry 5 built Ove, a dating app, and the lessons from what we learned building Ove are the kind competitors leave out of their cost calculators, because they never lived them.
Lesson one: the feature you demo is not the feature that costs. Matching looked simple. The real work was moderation, reporting, trust and safety, and the invisible machinery that keeps a community from turning toxic on day two. A dating app is a safety product wearing a fun interface.
Lesson two: real-time is a different animal. Chat, presence, and notifications sound like one feature and behave like ten. They change your backend, your costs, and your testing. The demo works on one phone. The product has to work when two thousand people message at once.
Lesson three: empty states decide launch. A social app with no users is a ghost town, and no algorithm fixes an empty room. If you are weighing a community product, our notes on how to build a dating app exist so your budget respects the hard parts before the pretty ones. Ship the safety and the seeding, then the sparkle.
The hidden complexity that quietly inflates a mobile app budget
The overruns founders remember never come from the headline feature. They come from the unglamorous layer underneath: the parts of hidden mobile app complexity that no wireframe shows and no first quote fully prices.
Performance is the first tax. Users abandon slow experiences with brutal speed: Google research found that 53 percent of mobile visits are abandoned if a page takes longer than three seconds to load and the same impatience punishes a sluggish app. Speed is not a polish task at the end. It is an architecture decision at the start.
Then come the states nobody demos: offline behaviour, expired sessions, half-finished uploads, a payment that succeeds on the bank side but fails in the app. Each is a small feature. Together they are a third of the real work, and they are where cheap builds quietly cut corners.
The last hidden cost is not knowing what happened after launch. An app with no instrumentation is a car with no dashboard. Getting your mobile app analytics setup right from day one is what turns opinions into evidence, so your second version is built on what users did, rather than on what the loudest person in the room assumed.
Submitting to the app stores: what actually happens
Getting built is not getting live. The final gate is review, and it has its own rules, timelines, and rejections. Knowing what submitting to the app stores really demands is what keeps launch day from slipping a fortnight.
The good news on timing: Apple states that on average, 90 percent of submissions are reviewed in less than 24 hours so review is rarely the long pole. The delay is usually rejection and resubmission, not the queue.
Rejections cluster in predictable places: missing privacy labels, a login that reviewers cannot get past, payment flows that skirt the store rules, and permissions you ask for without explaining why. None of these are hard. All of them cost days when they are discovered at submission rather than planned in design.
Google Play is generally faster to accept and stricter after the fact, with policy checks that can pull a live app later. Treat both stores as launch partners with standards, not as a printer you press at the end. Prepare the store listing, the screenshots, and the privacy answers weeks early, in parallel with the build.
How to brief a mobile app so the quote is real
Everything in this guide points at one lever you control: the brief. A strong brief is the cheapest thing you can make and the most powerful, because it turns five disagreeing quotes into five comparable ones. Knowing what to include in a mobile app brief is the closest thing to a superpower a non-technical founder has.
A brief that earns a real number answers these before a studio has to ask:
- The one job: the single workflow the app must nail, described end to end.
- The users: who they are, how many, and what they do on day one.
- Platforms: iOS, Android, or both at launch, and why.
- The must-haves versus the nice-to-haves, listed separately and honestly.
- Integrations: payments, maps, login, messaging, anything with an external key.
- The budget band and the launch date you are actually working toward.
Naming a budget is not weakness. It lets an honest studio tell you what fits, what does not, and where to cut, rather than reverse-engineering a proposal to whatever they guess you can pay. The best partners scope to the truth. Give them one.
Already know your one core workflow? See how our MVP development works, or keep reading for the questions founders ask most.
Frequently Asked Questions
How much does it cost to build a mobile app in London?
A mobile app in London usually costs between 40,000 and 250,000 pounds, and at Foundry 5 most first builds land between 40,000 and 90,000 pounds. A lean MVP with one workflow sits at the bottom, while a multi-role product with payments and integrations climbs toward the top. The specification sets the number, so a clear brief is the fastest route to a firm quote.
How long does mobile app development take?
Most mobile apps take three to six months to reach a solid launch. A focused MVP can ship in 10 to 16 weeks, while a complex product with many roles and integrations runs six to nine months or longer. The strongest lever is scope: freezing the specification before the build starts protects the timeline far better than adding developers later.
Is React Native good enough for a production app?
Yes, for most apps. React Native runs production apps at Meta, Microsoft, Shopify, Discord, and Coinbase, and it lets one team ship iOS and Android from a shared codebase. Native still wins for high-frame-rate games, heavy real-time hardware use, or apps built around brand-new OS features. For the typical founder product, React Native is the faster, cheaper first move.
Should I launch on iOS or Android first?
If a shared codebase like React Native fits, launch on both at once, because the extra cost of the second platform is small. If you must choose, follow your users: iOS tends to lead for paid consumer and premium audiences, Android for global reach and price-sensitive markets. In the UK, most consumer apps benefit from launching on both stores together.
What should I include in a mobile app brief?
Include the one core workflow, who your users are, the platforms you need, your must-haves versus nice-to-haves, every integration, and your real budget and launch date. A brief with those six things turns vague quotes into comparable ones. Naming a budget is not a weakness: it lets an honest studio scope to the truth instead of guessing.
Conclusion: your mobile app development London decision in one move
Strip away the frameworks and the cost bands and one move decides the rest. Mobile app development in London rewards founders who freeze the specification before anyone starts building, because scope, not the postcode, sets your price and your timeline. Foundry 5 builds this way on purpose: a rigorous discovery that hands you a clear scope is us protecting your budget before we spend a pound of it.
If you are building a mobile app as a startup, SME, or growth-stage business and want a partner who stays after launch, book a free 30-minute discovery call with Foundry 5. No pitch deck. No pressure. Just a direct conversation about what your app should do, what it should cost, and how fast it can ship.
