Wow John, you would really consider doing 3 salsa classes in one night, well to be honest I would too (hard-core)
I am an advanced dancer too and while it will be interesting to do beginners/intermediate classes, I find it more useful to dance socially with people of this level to improve my all-round salsa.
But if you are looking to become a teacher, my friends tell me that doing beginners/intermediate classes is good way to pick-up tips and ideas for classes. So if you are heading down the teacher root perhaps the prices should not matter (!?).
I have in the past and even to this day been in advanced classes with students who are not at that level either, and it does slow the progress of the class.
I am looking forward to seeing more advanced salsa classes in Cardiff; it will help to improve the overall standard of dancing her.