Me again
Tricky one this...there have been a few threads on the matter and of leaving (or not!) debt in general to service when resident here and no doubt you'll get responders from all sides....
Speaking personally, I'd make every effort to pay off as much if not all of the UK debt before you leave...
one less worry on the wallet and heart...,
failing that, keep open a uk bank account, pay what you need (plus service/transaction fees) into that each month by direct international transfer from your NZ bank account..
(threads on that here too!) and use that to service your UK credit card ASAP...
I doubt if any NZ bank will let you do what you're proposing.. that but then again...see... round and round you can go...
cheers