Can't comment on CATS, but I've done my ATPLs so far with BGS (just booked the last set of exams).
Good Parts of the course:
-The material is well set out and the CBT is very easy to use and to track your progress on.
-The Brush-up courses are excellent, the instructors are brilliant at what they do. I found rather than being purely revision courses I was learning quite a bit as well.
-The feedback system seems to work very well, they have a good idea of what you can expect in the exams and you can prepare well for it. This includes those rare questions where the examiner has a slightly different answer to what you might expect.
-The QB I personally found very useful, it splits each subject down into individual topic scores allowing you to quickly and easily identify any weak areas to concentrate on. You can also test yourself purely on these areas if you so wish.
-If you are looking to do it all quite quickly I'd say 2 sittings of exams is better than 3, it all adds up to roughly the same time away but theres less of a mess around factor when only doing it twice (assuming no re-sits).
-You have use of the ATP forum, which is frequented by the instructors at Bristol, a useful tool if you have a burning question.
-The technical support for the CBT is excellent, I had an issue with mine recently (turned out to be an issue with my computer taking a few hours to catch up with the software) and they were extremely helpful in rectifying it over the phone/email.
Disadvantages:
-As you mentioned above; price and non-permanent access to the updates.
-Splitting the exams into 2 sittings is quite some workload, the 1st module is 8 exams which is quite a lot to study for in one go (albeit I found them easier than I'm finding mod 2). Also granted here you don't have to sit the exams in 2 sittings, you can split them into as many sittings as you like within the limits.
The assumed knowledge in the ATPLs is probably around GCSE level, so with a science background you may find that some of it is teaching you to suck eggs. I wouldn't treat it as such though, I found thinking too deep into some areas just lead me astray and I just had to accept what was written in the text book.
As for BGS not allowing you to start before receiving your licence, have you phoned and explained your situation? I have a sneaking suspicion the girls on the desk may be happy to send you the materials while you're waiting on your licence, don't hold me to that though.
Good luck with it
