The best bet is to either buy the Tevor Thom books or the Jeremy Pratt (AFE) books. Majority of us have used either set. I personaly used the AFE books.
They will set you back about £20 each and there is six of them. For exam practice you can register with
www.airquiz.com and sit as many mock exams as you like.
As for the real exams you have a couple of options:
1) Sit them at your local school for about £20 a pop
2) If you plan to do the flying in the states, sit the exams at the school over there. Most US based JAA schools include the exam fees in the course fees.
Either way make sure you pass each exam with out having resit them more than 3 times. Otherwise you will end up having to pay a hefty price for the CAA to write a bespoke exam for you to then go and sit in Gatwick