Awesome, New Zealand definitely looks amazing and i'd love to visit someday.
I think from speaking to various people when we were in the deciding phase, is that if it interests you then you just have to go for it. If it turns out to be a wrong choice then so be it, just move back to the UK, but too many of my friends talked about Australia but then had kids and decided they'd missed the chance as it was too disrupting, then again they keep looking back saying things like "if only we'd done it x years ago before kids were y age". I know you don't intend on kids so not a factor, but there'll always be something holding you back if you let it.