I have just spent the last 4 days doing all 6 theory exams plus my FRTOL practical and I passed all quite comfortably. I am still about 2 months away from actually starting flight training (in the USA) but I wanted to take the pressure off so I did the exams in the UK before going.
For the theory exams, I did them through a combination of self study (AFE books) and then a 2 day revision course / exam sitting with a ground school. The ground school also provided a set of summarised notes which were very useful. The revision course basically assumed I had done self study and gave a run through of key areas or areas where I wasn't clear. I would strongly recommend starting to read early as I found it took a while to get my head around some of the things without a practical working knowledge.
For the FRTOL, I also did a two day course with the exam at the end of the second day (today). This was invaluable to me as I had no experience of UK RT procedures and some things were very hard to visualise out of a book.
In the end, if you intend flying next year then you should consider doing the exams sonner as suggest by mcgoo. I am not a member of any club in the UK (in fact I don't even live in the UK) but there is no problem with doing the exams anyway. I can't tell you what a great feeling it is to know that I won't have to worry the exams when I start the actual flying. Flew into UK on Wednesday night and leave Monday morning with all exams (and medical) out of the way. Woo hoo.