NZ should be no problem for a Triumph -- it's a popular make there. The new bikes as far as I know are essentially the same for all markets, so you should not have a problem.
Thunderbike in Nelson would be my first recommendation for a dealer on the South Island. The owners (John and Ian Fitzwater) are serious bike guys, Triumph fans, and also run a tour company (gotournz.com). I will shamelessly promote them since I toured with them in 2004 and they were simply fantastic.
And NZ has among the best motorcycling roads I've come across...
