Each time you log onto the BGS Online Question Bank a menu appears with the following options:
ATPL(A)
ATPL(H)
CPL(A)
CPL(H)
ATPL(H) to ATPL(A)
So yes it probably is worth while for the CPL(A) question bank. However I am unsure of its suitability as I've only used the ATPL(A) databank.
In regards to the quesiton bank in terms of ATPL(A) questions, it seems to be pretty good, especially for Meteorology, General Navigation and Instruments.
However as the previous poster states, do not use it as sole reference to study. Study from your books and use the question bank only as a guide and also to get used to the style of questions that the JAA give you.
One thing to note though is that all questions in the databank are 1 mark each. In the real exams some questions will be weighted to 2 or even 3 marks per question (I noticed one 3 marker in Met this month), the weighted ones will probably happen to be the more difficult or time consuming questions as well.