Hi
mcewenaj and welcome to KB.
Do get your full UK driving licence before coming to NZ. It will save you a lot of difficulties and expense. As has already been stated, you can use it for 12 months without any problem.
A providional licence is worthless out here.
BUT motorcycling is a serious subject and starting from no experience on a 250cc bike on NZ roads with NZ drivers is like having a Death Wish and best avoided.
In NZ it is very easy to get mobile on a 250cc motorcycle. All you need to is show up with ID and take a Basic Handling test. FRom what I have heard, no one has ever failed! Yes it's that tough and then you are free to go out on the open road with no skills and experience and take your chances.
Best advice from me is to book or even pre-book yourself on a beginners motorcycle training course asap.
LOOK here's some here:
http://yellow.co.nz/search.ds?what=m...newSearch=true
This will not be terribly expensive and may well turn out to be a very wise investment to enhance the longivety of your life and also make your motorcycling experience a pleasurable one.
Good luck.
BTW: AS nice as it is: Queenstown is not one of NZ's larger Cities. If you go there first you may be able to get a bit of skiing in before the season ends.
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