After doing some research I chose CATS. Money was a factor but I had heard some good reports.
I have to say I feel let down by the service they have delivered. After all we are paying for a service & not simply access to a web-site.
Brush-ups are really just sessions of practice papers - understandable to an extent but in reality you spend most of the week alone in the class with the other students. I found that frustrating - as did others I was on the course with.
The student support - via email - has been inconsistent in that some subjects seem to be well supported but others not so (one can only assume this is to do with the approach of individual tutors). In the lead up to the exams I have found the Bristol instructors to be of more help via the QB forum than the folks I actually paid to help me along!
Compared to the Bristol set-up (which I received a demo of before signing up with CATS) CATS really doesn't compare. Yes, it's double (ish) the price but I really do think you get what you pay for.
Anyway I paid my money & made my choice - just thought I would share my experience.