TJF
Personally I would opt for the 2 modules route, purely because if you did 3 modules you will probably feel like there is no end in sight, it's alot of hard work, even with Bristol only having 6 subjects in Mod2 it alot, but having to do 5-5-4 or however many are in each module would be very tedius, this is only my view, and you may say a tad contradictory saying it's alot of work but opting for 2 modules, but at least with the 2 modules you feel you have broken the back of it after Mod1.
Regarding Bristol.gs
Again, I cannot fault them one bit, superb instructors, notes excellent, support great via the forums, evidently I cannot compare to other providers as I have only ever gone with Bristol but they will get you through, the 2 week crammers are fantastic and prepare you for the exams very very well, you're in good hands
Dean