Welcome to TSR!
I'm also applying for medicine now (as a postgrad though).
All medical degrees in the UK are basically the same in terms of how good they are and the result of it. Wherever you go, you're still getting the same qualification (all the unis have to meet GMC criteria).
In London, there are a number of different places you can study medicine:
UCL
Kings
Barts (Queen Mary's)
St George's
Imperial
Each one has their own criteria which you can look up on their websites.
Good luck with it all!