I would like to request one feature that many of us in London would like to have and that is to follow the London unified prayer times. There is an API that can be used so you can add it to your app. Many of us Muslims who live in the UK, especially in London follow the East London Mosque. And it's very difficult to find an app that follows this method. I will provide two links, one with the API and another with the East London mosque website explaining the prayer times and how they are calculated. The East London mosque is one of the biggest mosques in Europe and it only makes sense for this to be added in your app.
How the prayer time is calculated in London
Barak Allāhu feek.