How to Choose an App Development Agency in London: 12 Criteria

The verdict in three sentences

When three agencies quote the same application between EUR 35,000 and 95,000, the gap rarely comes from talent: it comes from the number of days actually planned, the day rate (GBP 550 to 900 for London agencies in 2026, versus EUR 450 to 750 in a French regional city such as Bordeaux) and what is included or excluded (testing, warranty, documentation, hosting). The cheapest quote is often the one that underestimated the days or quietly subcontracts offshore. Compare quotes on 12 measurable criteria, and get code ownership in writing before signing anything.

Reading a quote: day rates and days

A quote always breaks down into days multiplied by a rate. Reducing every proposal to that formula reveals the gaps immediately.

Take a business application estimated at 110 days. At an average blended rate of EUR 550, that is EUR 60,500. A EUR 35,000 quote means either 64 days at the same rate (scope underestimated by 40%) or 110 days at EUR 320 (offshore production). These are 2026 ballpark figures.

The 12 criteria for comparing agencies

An agency ticking 10 of 12 criteria at EUR 60,000 is almost always a better choice than one at EUR 35,000 ticking 5: the missing days come back as change requests, often worth 30 to 50% of the original quote.

Mini case study

Emma, managing director of a 45-person wine distribution SME in London, receives three quotes for an order and stock management app: A at EUR 35,000, B at EUR 62,000, C at EUR 95,000. Asking for the breakdown in days, she finds that A plans 70 days at EUR 500, B 110 days at EUR 565 and C 140 days at EUR 680 (including a mobile app she did not request). A includes neither testing nor warranty: adding them would cost about EUR 9,000, and the underestimated scope points to EUR 15,000 of change requests. A's real cost is therefore close to EUR 59,000, without code ownership. She picks B, which assigns the code, includes a 3-month warranty and accepts a 0.5% weekly late penalty. With the mobile module removed, C drops to EUR 78,000, still EUR 16,000 above B.

FAQ

What day rate is normal for a London agency in 2026?

A blended rate of GBP 600 to 750 is consistent for a local team mixing mid-level and senior profiles. Below GBP 400, ask where the code is really produced.

Is code ownership automatic?

No. Without an IP assignment clause, the agency keeps copyright in the code it writes. Insist on assignment, often included at no cost, sometimes charged at 5 to 10% of the project.

How much acceptance testing should we plan?

Between 10 and 15% of development time, i.e. 2 to 4 weeks for a EUR 60,000 application. Testing should run on an environment identical to production.

Are late-delivery penalties realistic?

Yes, if they are symmetrical: the agency commits to a date, you commit to approval turnaround of 3 to 5 business days. A cap of 10% of the contract value is standard.

Should we reject all offshore subcontracting?

Not necessarily. A 20 to 40% share given to a named team, with a local tech lead accountable, can cut cost by 15 to 25%. The problem is hidden offshore work.

Let's scope your project. Send us your specification or the quotes you have received: we will return a detailed estimate in days per feature, with code assignment and a 3-month warranty included. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.