Metz 45 CL-4 battery pack battery replacement

I have a couple of Metz hammerhead flashguns that I think are just great. But...

The NiCd batteries in the battery pack are just about stuffed. I'm looking to change them, preferably for NiMH, but I can't get the pack apart to do this. Anyone done such a thing? In theory it seems entirely possible, and there should be no problems voltage or charging wise. The problem just seems to be down to how to get the pack apart without trashing it.

You can always buy a battery holder 45-39; costs $25 at B&H, could not find a price in the UK.

I can get a holder for Alkaline batteries from eBay for £12 no problem. Holders for Nicads / Nimh are different because they have different connector points because of the difference in voltage. I have replacement Nicad batteries ready and waiting but I can't get the holder part without risk of breaking it. I'm hoping that I'm just missing something on the construction, but if not, I'm hoping that someone can tell me which bits to break.

The end of the battery pack that normally sits in the flash (the bit with the sliding 'switch') will unclip and remove to reveal a screw. Undo this screw and the pack will separate.

I am happily using mine recelled with NiMh cells. It is tricky to reassemble and make it all fit again as the original tags are spotwelded in the correct orientation, the replacements will be (if like mine) at right angles. I also successfully use a 'Sonia' brand adaptor for NiMh AA cells as a second pack.

I was not aware of any different connector points??