I’d like to thoroughly recommend the superb wildflowers app for iphone/itouch with its wonderful ID key. The app includes more than 1000 wildflowers of France and Western Europe, which means the vast majority of British wildflowers are featured. You can choose between English, French and German.
I’ve been using it for some time and updates with new species are regularly provided. For the future, could do with some distribution maps but this is a fab start.
Guaranteed to get you out there identifying stuff. More here
Forgot to mention: you can also add notes about each species (where you saw it etc) which I’m finding very useful.Some possibly unrelated posts