For anyone planning a holiday/trip to New Zealand I would highly recommend staying in a holiday house/home (often called ‘bachs’). We have often found they can work out a fair bit cheaper than hotels/apartments, and you get all the comforts of home and can live like a New Zealander for a while!
The best website we have found and have used in the past is: Holiday Houses. The site is very easy to use, owners are usually very responsive, booking is easy and we stayed in an absolutely amazing place from this site as part of our honeymoon 2 years ago.
Other sites that may be of interest include: