The most difficult part I found was actually locating my local group and having the nerve to turn up at a meeting. The 'demonatration drive' was fun, but then the first 'assessment' really hurt ! Basically I found the whole thing really enjoyable and stayed as an active member of the group for quite a while untill marraiage and family took up my time.
I used to be an examiner for RoSPA Advanced Drivers. Most people found the commentary part of their test the hardest! Chat to them about weather / sex / sport etc etc & they wouldn't shut up. But as soon as you asked them to talk to you about what they were doing as they drove down the road then they became more nervous than a nervous thing that's just been awarded Professor Of nervous....(etc etc etc......)
The commentary drive is now optional on the I.A.M. test, pity they dumbed down.
Don,t expect reduced insurance after you pass your test, when I got my I.A.M. certificates I rang every company that advertised in the I.A.M. magazine and they were all more expensive than the one I already had. Just do the usual and shop around.
It is worth doing the I.A.M course and test, it will make you a much safer, more economical and even faster driver.