So I've just tested everything - GP32s and GP2x are in perfect working order. Both Wiz batteries are dead so they only work whilst plugged in to the charger - and one of them won't stay turned on after the power switch is toggled. This was an early dev unit (also has two directional pads instead...
None of them would come with original packaging - I don't use any of them anymore and I'd rather pass them on to a loving owner than chucking them out .