Hey Pete
I wrote some stuff on this a while back
www.seabreeze.com.au/forums/topic.asp?TOPIC_ID=61696&Lots of spots around Auckland although the wind is the biggest enemy. Great time of the year with brisk offshores to keep you warm. Not sure where you can hire SUP stuff from but I am pretty sure the other kiwi boys on this forum can help you out there.
Make sure you get yourself to Raglan for some waves if you get a chance. 3 epic point breaks - well 2 - the other is a bit lame most of the time I reckon. 2 hrs south - or 1.5 from the airport. Its unreal. Here is some footage from a few weeks back.
http://www.surf2surf.com/video.php?id=278How cold is it - it will be a lot colder than here for sure. Pack yourself your best 2/3mm seam sealed baby. It should get you through the next few weeks.
You will need a hire car to get to the waves for sure - public transport options are few and far between. Its about 45mins to the West Coast beaches form down town Auckland. Watch out for the stupid rule of "when turning left give way to everyone" The insurance companies love Australian drivers due to that rule!
If u have any specific questions happy to answer those.
Enjoy!