It was a while ago I made this thread. Having done the course myself now, I would say that the course is good. The lady we had in Birmingham was brilliant. And it is about the experience of questions under timed conditions, getting used to as many times of questions as possible, and being told the technique to use. Essentially, yes, you are paying nearly 300 quid for a huge book with all the information in it, but that's not to say the woman that ran the course wasn't a massive help.
I do think however, I then began to rely on the course completely. Assuming that just doing that and a few questions from the 600 Q book was all I needed. This wasn't the case hence my 627.5 average.
Is it necessary? No.
Would it help? Yes - especially, if your feeling unconfident, new to the whole thing, and generally, don't even know where to get started.