I finished my PPL recently and would wholeheartedly recommend EGLM if you can stand driving that far. Three long grass runways (never a problem with crosswind limits) which drain well, although they aren't very flat so that keeps you on your toes.
The best part about learning at a dedicated GA airfield (something that Biggin is definitely not) is that you can almost always just power up and go. Somewhere like Biggin you will often need to wait in a queue to line up, and jet/commercial traffic will always get priority over PPL training flights. Then when you're in the circuit you'll get told to orbit to allow something else to join, or be told to go around so that a jet can line up and take off. I've heard plenty of stories of students spending £200 on a lesson and getting two circuits in.
The counter-argument people make is that those who train at 'big' airfields with full ATC end up being better on the radio. I'm not sure I agree with this - I find the RT at controlled airfields is just 'different' rather than harder. If anything one could say it's easier, since a lot of decisions get made for you - you just have to read back and comply.
Regards reading up beforehand, my instinct is that if you're paying £200 for a lesson then you'd be barmy not to do all the reading/prep that you can in advance. Further on down the course (nav) it amazed me when my instructor told me that lots of other students turned up for nav-ex lessons without having planned the route or having looked at weather/notams beforehand. Why would anyone pay £200 an hour and not do everything they could to make sure they got the most out of it?