Thanks to all.
So just to confirm. If I do a BFR ( say on a cessna in NZ ) before the expirey of 5 years I get to keep my ATPL without the need to write Air Law. This maintains the ATPL Status and allows me to fly for fun in NZ, however should I require to work on my NZ ATPL ( part 121) then I would need a 121 checkride.
Seems clear as mud.
Good luck to all in pursuit of it !