In reply to J Brown:
First of all, congratulations!
Flights to NZ are expensive, granted. A quick look on travelsupermarket and your profile (to see where you were based) and £1400 would see you and the wife on a return flight (Edinburgh to Auckland) for 4 weeks leaving on a random date in December (I think I picked the 23rd for whatever reason). Definitely go online rather than via a travel agency when booking flights
While that is a lot of money, from person experience of 4 weeks in NZ, the absolute best way of sorting accommodation and travel in one go is hiring a camper van. Camp sites are so well set up, and widely available, and even if you are off the beaten path, wild camping in a van is no great hardship. WAY cheaper then staying in a hotel, paying for all your meals in a restaurant, and hiring a car / going on individual tours. You also have absolute freedom on where you go and what you do.
I guess my message would be not to discount NZ based purely on costs of flights; it honestly is a country that is tailor-made for what you want to do. Oh, and if you and the missus can survive 4 weeks in a campervan together, you'll know your marriage is built to last
cheers!
rb