If your licence will be an FAA one...
Martyngorton,
If at all possible, try to have ALL your written exams out of the way before you go as that will remove a good deal of pressure from your sojourn in Florida and make your success in the flying training within your timescale more likely.
You can get FAA study material and a copy of FAR-AIM from the various pilot shops in the UK.
There is now a newly opened FAA examination centre at a company called 'Flight Safety International UK Ltd' at Farnborough. I know for certain that they now have terminal facilities there for taking FAA 'writtens' for CPL, IR, and ATP, so I imagine they may well offer facilities for taking PPL writtens also. (Until recently, you had to go to some place at Le Bourget). Give them a call: these are the details.
Flight Safety International,
Farnborough Airport,
Farnborough, Hampshire,
GU 14 6 XA
Tel: 01252 554500
They also provide facilities for having your fingerprints taken for the benefit of the TSA.
This set up at FSI Farnborough is brand new. I've been in there to make enquiries and it all looks very impressive. Clearly a lot of money has gone into setting it up. If you do use them, do report back here on Pprune to let us know how you get on.
Broomstick.