Approach your county police force, most forces do, or will do, advanced driving courses if asked nicely, I think they basically chop down the course they do for the class A training, you dont get to do certain things from that course though, like persuit etc
So, give them a try, at least you will get a youthful instructor, as I have found (Only my personal opinion) that IAM are mostly filled with the older generation.... Rospa is meant to be good as well......
Good luck with it, and tell us what you went for in the end!