Agree with Hef, can't go past Wanaka Heli. Top outfit, good machines, great instructors and learning enviroment. The guys down south at Southern wings are worth a mention too. I think South West Heli provide the training? Others Mark Law, Ric Graham, Doc Sutherland and Gavin in Te Anau.
I would tend to avoid large schools that treat you like a number and have student loans.