Hi,
I would say you should try and get a few flights (in light aircraft to begin with) by hook or by crook. Go down your local airfield and see if there's any part-time work going, or just pester somebody into giving you a flight ! That way you'll get to know how much you like being up front in an aircraft.
You're pretty young but its good that you've got a strong sense of what you want to be. NZ has always struck me as a great place to learn to fly, so, as I say, get down to your local airfield and start getting into the scene down there. You will probably meet a lot of interesting characters who can advise you.
From an education point of view, maths, physics and computing seem to be a good way forward.
If you want any more specific advice send me a PM.
Mungo