I did the Intermediate Track Day course last year, and I have to say that it was one of the best courses I've ever done. Mainly because Colin Hoad is an *excellent* teacher. I've had plenty of 20 minute sessions on track days, but the problem with those is they aren't long enough, and they're delivered by racing drivers - and the characteristics that make you a good racing driver (ego & aggression) make you a very poor teacher. Colin describes in detail the point of an exercise, then you repeat it until you properly understand what the car is doing underneath you, with pauses for further explanation, on both sides.
It also helps that he has a very professional set up and that Millbrook is a bloody impressive place!
I fully intend to go back and do the Advanced Track Day course this year."