clear blue water,
i believe you have got it the wrong way round, a CAA ATPL(H) was granted at 1200 hours total by virtue of hours alone (subject to the minimum elements e.g. 20 hours night), to the holder of a CAA CPL(H) no further exams were required, so everyone including me did CPL level knowledge, cos that was all we needed.
JAA ATPL(H) requires 1000 hours total including 350 hours on multi pilot helicopters (which in itself requires an instrument rating) and 100 hours night etc and ATPL level knowledge, so most people as I understand it who are going for the JAA CPL(H) are doing ATPL level exams at the start to avoid the need later.
whereas a basic JAA CPL(H) requires much less than this,185 hours total time including the various elements and CPL level knowledge.
people such as me who have a CAA ATPL(H) who would like a JAA ATPL(H) require 500 hours on multi pilot helicopters and if they have less than 1000 hours multi pilot have to demonstrate to the CAA a knowledge of flight planning which is laid down in JAR FCL, crucially though they DO NOT need ATPL knowledge, as their licence would be endorsed to show that the new licence was granted on the basis of CPL level knowledge ( so if you went fixed wing you would end up doing the ATPL exams, what a drag)
phew ! do peeps agree with this ?