For what purpose
If you are going there just for kicks and to do some private flying, then the smaller aeroclubs are the way, try to stay away from Ardmore Airport in this case and head a bit south. hamilton is good and the South Island is majestic.
However if you are looking to go on to an ATPL and a JAA one at that, there is a school in Hamilton which trains guys out of the UK. It's called CTC Aviation. I have no idea if they are good/otherwise but I do know they train prospective ATPLers from the UK.
Motueka near Nelson (sth island) is also really nice and they get all of the good weather!
One other thing. If you go to an operator in Taupo (middle nth Island) called Taupo Air Services, they train as well and the owner is a top bloke. You'll have no worries with training and there may be a job at the end if you choose to go commercial. Scenery second to none.
Cheers