Button,
Generally when my wife and I travel we book the first couple of nights and then wing it.. I hate letting my accomodation bookings manage my holiday. We did NZ, South of South Island for ten days in May a couple of years ago with two other couples and had no trouble getting digs on the fly. Have done the same with Tasmania, Japan and Europe.
There is so much to see in NZ and with 5 weeks you should be able to catch a fair bit. Enjoy, relax and go home safe.
