Well, Mrs Theboy and I finally attended the course on Sunday, and....
I can recommend it (almost) without reservation!

Two cars, an old Rover to do the understeer (and how), and an old 3-Series to do the oversteer (BMW was much more fun and much faster round the track, but not immune from understeer on lift-off!).
They put you in threes and you each go round a few times in each car, then have a bit of sit-down tuition, so consequently three hours went very quickly, rather than lots of standing round, which I feared would be the case.
Also a bit of practice at emergency braking/avoidance in non-ABS BMW and ABS Cavalier.
And finally a time trial, which I did very badly in....
Things I learned:
- Apparently apply the clutch if you oversteer (this works a bit)
- Wind lock off and on again in understeer (this really works!)
Main reservation: The oversteer tuition was very much aimed at the effects of power oversteer, and I got the distinct impression that, as this was the short course, they'd rather not talk about it too much.
There was another couple, a few 30-something blokes, and a handful of young lads who'd clearly been brought by parents for training (one brought his really fit girlfriend in skimpy top and denim hotpants, many crashes occurred when cars passing where she stood

).
Anyway, in summary, a very useful course for people of a wide range of skill levels, and as Paul said earlier in this old thread, do a course where you drive on a slippy surface, not a cradle course.