No experience of Bristol, but I did a distance learning PPL/IR course with PPSC last year.
The notes (particularly the air law) were a bit dry, and often needed clarification. However the support from the school was ALWAYS second to none, and the 5 day brush up course at the end of the DL course was excellent (and helped a great deal).
I passed all 7 PPL/IR exams... and surprised myself in so doing!