It is a JAA requirement that there is a classroom element to the studying and that a certain number of hours self-study are undertaken. By enrolling with a flight school and following their structure, this requirement is met.
As a note, Bristol do not do CPL(H) ground, only ATPL(H). The CPL(H) providers are CAPT, Atlantic (Interim system i.e. fixed wing bias) and Dragon.
Cheers
Whirls