The ATPL exams are only any use if you plan on getting an IR (and working in a multi-crew environment) within three years of passing your exams. If you don’t wish to get an IR, then the only point of the ATPL exams would be for your own interest!
If you did decide, after 5 years to go for the IR, you’d have to do the IR exams, if not the whole ATPL (depending …..)
The standard of the questions between ATPL and CPL is the same but the CPL syllabus is shorter (though not by much apparently!!). PoF is the same paper for CPL and ATPL as is, I believe, HPL.
However, with each exam being £63.00 plus travel costs plus expenses for brush-up courses, a shorter syllabus will be cheaper.
There are three CPL(H) providers; Atlantic (who are under the Interim system – I used them and they are good but it is very fixed wing oriented), Dragon (who have a helicopter specific course) and CAPT (also H-specific). Of these, only CAPT do an H-specific ATPL.
Bristol GS do interim ATPL(H) but not CPL(H). Glasgow has, I believe, ceased to do ATPL studies completely.
Hope that helps,
Cheers
Whirls