Just found this out, hopefully I can stop other people making the same mistake i did...
I purchased my camera 9 months ago when Nest were not in NZ and used a temp US credit card to pay for the subscription.
I figured now that they were in NZ I would change the subscription over to a NZ one which would allow me to have an NZ address.
However i've just been told by Nest support that you can't purchase Nest Aware for an overseas camera (say purchased in the USA) with a NZ credit card (note been advised Australian cameras are fine)
So if you want Nest Aware and the convince of paying with an NZ credit card, make sure you buy an NZ camera.