Many thanks to Adrian and sgc for their replies - that's a big help. I was struggling a bit, not having had any practical experience of the situation.
Nikki, it suits me very well to study from a book on my own, so long as the book is good and comprehensive and there are plenty of exercises to practise with. THat seems to be the case with the Kaplan books I mentioned, but the proof of the pudding will be in the eating - I'll let you know how I get on in the exam, which is imminent.
Some people may prefer to have pre-packaged lessons and deadlines set by a course provider, but personally I don't find that particularly helpful. With the Kaplan books you can simply work through the chapters in order.Obviously if you study on your own you won't have a tutor to turn to if you get stuck. However my experience with this question and this forum suggests to me that you can probably get as much help from other ICB members as you are likely to get from tutors if you come across a difficulty.
Best of luck!