Dealing with your questions in the order that I remember them:
PPL or NPPL I think the difference in min time is only about 10 hours so on that basis alone I doubt it's worth the savings. Looking longer term you may not want to fly abroad now but I bet you will before long (a good reason to learn to fly is the freedom to explore so why limit yourself to just the UK?). In addition why limit the training you receive good training initial and recurrent is vital so you might as well get as much as you can.
Ref the medical if you are reasonably fit (and I mean just basically healthy) you won't have any problems with the Class 2. Unless of course you are colour blind or have particularly poor vision or hearing so don't worry about it.
Turning to schools, certainly your nearest field is Biggin and doubtless the schools there will be only too happy to take your money. But also consider going a little further afield (Biggin is a killer on landing fees so that'll increase your training costs considerably) for example you might look at Rochester or Redhill since you might find things more cost effective (dunno about Rochester but at Redhill there are no landing fees for based aircraft - of course these are both grass field so you may have flying curtailed because of waterlogging this time of year Redhill is more sea than air port). Take the time to look around and find the place that best suits you and your wallet (the two are not necessarily linked). You are after all about to invest a lot of money and time in this flying malarkey, so its worth doing the research.
Lastly probably the most important thing is to enjoy the process I reckon a lot of people put too much stress on themselves worrying about going solo or completing the QXC or even the skills test. The point is its all flying and its all fun so enjoy it. Oh yeah and remember getting the ticket isn't the end its the beginning.