Yes, I know - I also find it really difficult.
Guess, an hourly rate somewhere between NZ$25 - 30,- (if you work in one of the major cities) might be a starting point.
Private practices have had a really difficult time over the last year and most of them have reduced staff massively, due to the changes from ACC. Therefore, they will be able to tell you what they can afford to pay you and you just need to see what your best offer is. Mind you, jobs are scarce.
And in hospitals, your rate will depend on how much responsibility you're going to have. They will pay you the same they pay other staff in similar/ equal positions.
The way the job situation is at the moment, you might just need to take what you get and then go from there.
Good luck,
Fyzzio