FlyAnotherDay,
I asked a similar question last year before a trip to NZ. You could search for it in the archives; got a number of interesting replies. My situation is a bit different to you, as I work as an ATPL(H) in the UK.
My flying there was limited by other things and some unhelpful weather. However, I did fly an R22 briefly at Wanaka Helicopters with the guy who runs this outfit. A thoroughly professional and experienced instructor - trouble is I can't remember his name and his business card has gone missing.
It wasn't my first exposure to mountain flying - but the way he approached instruction, I am sure that you would get value out of any training you did with him.
Not to say that there aren't lots of other good places/instructors in NZ - there is lots of opportunity to refine mountain flying skills there.
Best holiday I ever had by the way!
Helinut