MVP Development in London: From Idea to Launch in 90 Days

London is one of Europe's most vibrant startup ecosystems. But the graveyard of failed MVPs is deep — products that cost £50,000–£150,000, took six months to build, and discovered that nobody wanted them.

The problem usually isn't the technology. It's what gets built before the technology: the assumptions baked into the product without being tested, the features added because they 'seemed important', the decision to build instead of validate.

This guide is about building an MVP that actually works — meaning one that answers a real question about your market, as quickly and cheaply as possible.

What an MVP Is (and Isn't)

An MVP is a minimum viable product. The emphasis should be on both words equally: minimum and viable.

Minimum means you've cut everything that doesn't directly test your core hypothesis. Not features you don't want — features you want but don't need yet. Most founders find this painful. It requires saying no to good ideas.

Viable means it actually works for users. A buggy prototype that crashes isn't an MVP — it's a prototype. The product needs to deliver real value to real users, even if it's a narrow slice of your eventual vision.

Common MVP mistakes:

• Building too much ("we'll need this feature eventually anyway")
• Polishing too early (spending weeks on pixel-perfect UI before validating the core flow)
• Targeting too broadly ("it's for everyone" means it's optimised for no one)
• Skipping the problem research phase entirely
• Conflating MVP with prototype — an MVP is used by real users, a prototype is a demonstration

Before You Write a Line of Code

The decisions made before development begins determine whether an MVP succeeds or fails more than any technical choice. We spend the first week of every startup project answering these questions:

1. What is the single specific problem you're solving, and for whom exactly?
2. What does the user do today instead of your product? (This is your real competition)
3. What is the one core action that, if a user completes it, proves your product has value?
4. What would make this MVP a failure? (Defining failure criteria upfront prevents scope creep)
5. Who are your first 10 users, and can you name them?

If you can't answer question 5 — if you can't name 10 specific people who will use your MVP — you probably need more customer discovery before starting development.

The 90-Day MVP Framework

For a well-scoped MVP with a focused team, 90 days from kick-off to live product is achievable. Here's how we structure it:

Weeks 1–2: Discovery and Architecture

The first two weeks aren't spent writing code — they're spent making sure we're going to write the right code.

Discovery covers: reviewing your existing research and assumptions, mapping the core user journey end-to-end, identifying the critical path (the minimum sequence of screens and actions that delivers value), listing all data the system needs to store, and documenting every external dependency (payment providers, APIs, authentication services).

Architecture decisions at this stage include: technology stack selection, database design, API structure, and hosting approach. Decisions made here are expensive to reverse later — getting them right is worth the investment.

Weeks 3–6: Design and Core Development

Design and development overlap in this phase. We use a design-then-build approach at the component level: the designer produces wireframes and high-fidelity designs for a feature, the developer builds it, then we move to the next feature.

What gets built in this phase: the core user-facing flows, the database and API layer, authentication, and the most critical integration (usually payments or a key data source).

What explicitly doesn't get built yet: admin panels, advanced filtering, notifications, analytics dashboards, or any feature that isn't required for the core value delivery.

Weeks 7–10: Completion, Testing, and Hardening

The second half of development focuses on completing secondary flows, fixing bugs found in internal testing, and making the product production-ready.

This phase includes: completing any incomplete user flows, adding error handling and edge cases, writing automated tests for the core flows, security review (input validation, authentication hardening, HTTPS), performance testing against expected load, and creating a deployment pipeline for continuous delivery.

Don't skip the security and hardening work even under time pressure. A hacked MVP that leaks user data is a startup-ending event, not a recoverable incident.

Weeks 11–13: Soft Launch and Iteration

Launch to your first cohort of users — ideally 20–50 people you've already spoken to. Not a public launch, not a Product Hunt launch: a controlled release to people whose feedback you'll actually process.

Instrument the product with analytics from day one. You need to know: where do users drop off? Which features do they actually use? What actions precede them churning? What actions precede them inviting others?

Expect to make significant changes based on the first two weeks of real user feedback. Build time for this into your plan — most MVPs need at least one round of major pivots before they're ready for broader launch.

Choosing Your Tech Stack

For most London startup MVPs, the right technology choices are boring and proven rather than novel and exciting. Here's what we recommend and why:

We explicitly don't recommend: microservices architecture (premature complexity for an MVP), GraphQL (REST is simpler and fast enough), or novel databases (Postgres handles most startup use cases without the operational complexity of specialised alternatives).

The Build vs. Buy Decision

Before building any feature, ask: does a mature, affordable third-party solution already exist? Using existing services for non-core functionality is almost always cheaper than building it yourself.

• Authentication: use Clerk, Auth0, or Supabase Auth — don't build it
• Payments: use Stripe — don't build it
• Email: use Resend, SendGrid, or Mailchimp — don't build it
• Search: use Algolia or Meilisearch — don't build it (unless search IS your product)
• File storage: use AWS S3 or Cloudflare R2 — don't build it
• Video: use Mux or Cloudflare Stream — don't build it

Your team's time should be spent on the features that are unique to your product — the ones that can't be bought off the shelf. Everything else is undifferentiated plumbing.

Budgeting Your London MVP

London MVP costs vary significantly based on scope and team. Here are realistic ranges:

The right tier depends on your market. B2B SaaS selling to enterprises needs a polished MVP — design quality is a buying signal. B2C consumer apps can often start leaner because users are more forgiving in early access. Internal tools can be deliberately rough.

How to Know if Your MVP Worked

Define success criteria before you launch. Typical MVP success metrics for different product types:

• SaaS product: 3–5 paying customers within 60 days of launch at a price that covers unit economics
• Marketplace: 10+ transactions in the first month, with repeat buyers
• Consumer app: 30-day retention rate above 20%, qualitative feedback indicating a 'must-have' feeling
• Internal tool: 80%+ of target users active weekly within the first month

If you haven't hit these markers in 90 days post-launch, it doesn't necessarily mean the product is dead. It means you need to understand why and decide whether to pivot, persist, or stop. The MVP has done its job — it's given you data.

Common Reasons London MVPs Fail

Based on projects we've inherited and rescues we've done, these are the most common failure modes:

1. Building too much before validating the core assumption
2. Choosing the wrong technology for the stage (over-engineered infrastructure for 100 users)
3. No analytics — launching blind and guessing what users do
4. Founder not talking to users after launch (letting the product speak for itself instead of listening)
5. Running out of runway before getting to the insight that would have pivoted the product
6. Building for investors rather than users (demo-ware instead of real product)

The common thread: prioritising building over learning. The MVP is a learning instrument. Treat it like one.