Hate to say it, but the texi isnt an advacned driving course., it will be fun, it will be timed, but sorry, I dont see it as a course.
The best ones out there...
anything by peter finlay, murcotts, ian luff, John Boston
and not sure if he still is around, but Aaron McGill's automotion
the first 3 guys and their companies offer at least 3 stages of courses. As Cass said - theres stage 1 and 2 and once you have done them, you can go and do stage 3.
you can then go on and do a 2 day course with Peter and Luffy, which then is more track orientated and can allow you to get your CAMS PC licence but these are quite expensive but certainly worth the money if you are going down that way.
Even some of the tracks and places, like EC, OP and HART (in St Ives) have their own courses and instructors.
It is certainly worth doing, good on you for looking into it mate!