snapper,
Try to find someone who did their PPL a while ago, and has a copy of the old version of the Confuser. This contained a written radio test which is very similar to the one you'll do. I have no idea why it's been removed from the latest version of the Confuser.
The r/t test really is nothing to worry about though. Don't bother with Thom. This is one of the few Thom books that I would recomend you save your money by not buying - it's different to CAP413 in places, and it's the phraseology in the CAP which the exams are looking for.
If you're getting close to gaining your license, you should be confident enough to know how to use the radio by now. The reading that you'll need to do will mostly be to refresh your memory and collect everything together, rather than to actually learn anything new. The only obvious exception is position reports - no one will ever expect you to give a position report "correctly" except for these tests, so you'll need to learn the correct way of doing it.
If you're still unsure about anything, ask your instructor - he's there to help!
Good luck!
FFF
-------------