I'm also studying with Bristol, in addition to the above post, if you write to, e-mail or phone BGS asking for info, they'll send you a nice little intro pack with examples of their course notes, and a credit card sized CD which has a demo of their 'interactive' notes system. The CD also has various videos and animations to help explain some of the harder parts of the course, such as gyros.
Remember that after each of the two modules, you must do a two week revision course at whichever school you decide to go with.
Also worth doing a search for 'distance learning' or 'ATPL course'. You'll get opinions about all of the different schools.