I think any school is what you make of it. If you put the effort in you'll get the results back out. If you're able to self motivate there's no reason why you shouldn't get decent results with CATS. What is good is that responses to email questions are usually pretty quick, the full time team are really knowledgable and the guest lecturers are a good laugh as well as being able to impart a real sense of what's happening out there in the big wide world.
I would completely agree with the above. Some of my own thoughts on CATS below. I should say these are my own opinion, but also shared by some others on the brush-up I attended recently.
Overall my experience of CATS was a mixed bag. The brush-up courses are a bit lax - no joining instructions are sent with the result that I (and a couple of others) arrived at Luton at around 0800 on the first day, only to find that the instructors/staff roll in around 0930. In fact on some days teaching didn't really get going until 10 or so. I felt more could have been achieved in the time. You're booted out at 1730 sharp as that's when the office complex shuts, so I should have thought starting around 0830 would have been better.
The venue itself is very nice. A modern office complex in a slightly soulless industrial estate in Luton but with a decent on-site cafe. Easy to get to from the station for those commuting and accommodation close by for those staying (Luton is well connected by rail, you can comfortably commute from London). I understand there is the option (at additional cost) to attend brush-up courses in Gatwick. I haven't done this so can't comment on the Gatwick venue.
In terms of the course itself, the instructors were again a mixed bag. The CGI (Dan) was excellent. He seemed knowledgeable, and well prepared for the subjects he taught us. A couple of the 'guest' lecturers were clearly less well prepared. I don't want to name names but one in particular was very out of his depth, and actually gave a few explanations which then turned out to be wrong on a close reading of the notes.
That said, I felt some of the other students put on a pretty poor showing. From some of the questions that were asked it was obvious that some had done very little pre-reading. The brush up is, after all, a course meant to consolidate your own learning. If you turn up without having read anything on the subjects you can't expect to get much out of it. Quite a lot of time was wasted explaining the very basics which clearly wasn't the fault of the school.
The CATS notes as I eluded to in my previous post, weren't brilliant in my opinion (although some others had used them and seemed happy with them). I bought some Bristol notes second hand and used these. On an inspection side-by-side with the CATS notes the BGS ones are clearer in my opinion.
As another poster mentions above, having access to more than one school's notes is a good idea as invariably each will have different strengths and having concepts explained in several different ways definitely helps with understanding.
I have also found the email support helpful and responsive.
Overall I would recommend CATS - with the qualification that I wouldn't rely solely on their notes, and on the basis that you're prepared to put the work in yourself to really understand the topics before attending the brush- ups. The flexibility and low price outweighs the disadvantages in my opinion.