We called Spaceships and decided to try the local panel beaters for an estimate, and were happy (as happy as you can be after reversing into a stationary object and messing up a hire car) to be told that the bill will only be NZ$350 (Euros 200).
So, now we have an unexpected bill, and overnight stay in Greymouth, but at least we didn't have to get a new panel, or fork out NZ$1000. OK, but still very annoying, and I feel very silly.
Debs