Hi,
I never even thought about that one, we're wanting to buy a car as well and move around.
I would imagine you'd be OK as loads of people go travelling and dont have a permy address.
Perhaps there's an online system? Have you been onto the NZ DVLA site?
http://www.nzembassy.com/info.cfm?c=...go&p=61604
I had a quick squizz but couldn't see anything about it, you might have more time at the mo to look through it all.
I do know that you can only drive in NZ for one year then you have to sit a theory test otherwise your licence becomes invalid. Apparantly it's pretty easy as my friend did it when he moved out with his Kiwi missus.
Let me know if you find anything out, when I get a bit more time I'll look through as well.