For legal requirements check LASORS 2006 (
www.caa.co.uk) download. For training a JAA PPL(H) with a JAA PPL(A):
Flight training credits:
10% total time (Fixed Wing) or a maximum of 6 hours (leaving you with 39 to complete the licence)
Ground Exams Credits
All you need to take are:
Aircraft General / Principle of Flight (Helicopters)
Flight Performance & Planning
These are the minimum regs.