Beagle has a point in regards to the exams. But as for the exam fees... the local flying club here charges thirty notes per exam and that is for fully paid up student ppl members. So another £11 wouldn't break the bank.
You may have to join the club in order to take the exams but you would be upon returning from the USA in any case as you'll be hiring aircraft from the same club within a month of your return to the UK.
When I did my PPL I used the Trevor Thom and PPL Confuser probably because they were the only material that were aimed at students back in those days... Now in this day and age you can purchase a couple of different sets of Textbooks and even a fancy CD-Rom package. I personally would stick to the books as it'll save you something like £250!! Another good point about books... you can read them on the bus / train if you don't drive to work...
Best wishes,
Charlie Zulu.