The JAA requirement is that the mandatory 35 hours of flight instruction (including the 10 hours solo and the qualifying cross-country) must be completed on one type of helicopter. The remaining 10 hours experience required for licence issue may be completed on any type. The EASA rules (post 1 July) are slightly different in that the mandatory flight instruction is increased to 45 hours and you must complete 35 of those hours on the same type of helicopter as the one used for the PPL(H) skill test. Which set of requirements you need to abide by will depend upon whether you will be applying for a JAA licence (pre 1 July) or an EASA one (post 1 July).