You can study for the ground exams in your spare time - they're not too difficult. My tip to you is to buy the JAR PPL Confuser, which is a collection of sample questions for the PPL exams, and work through that as you study - that way you'll know what to concentrate on and what is bull!!!!. You can take the exams at most local flying clubs; if you're not a member there will probably be a nominal charge. The only thing you should bear in mind is that you have to complete all the flying within I think 24 months of passing the first ground exam, but that shouldn't be a problem in your situation. One more tip - don't expect to get a PPL in the USA and then just come back to the UK and hire a plane straight off. Things are very different in the UK and you will probably need a few hours extra tuition when you get back. Good luck.