I just bought a MSR Hubba Hubba tent, though it's still in the mail so I don't know how it will work out in the field. While researching tents, this one and the Big Agnes Seedhouse both had great reviews, but the MSR seemed to better fit my needs. One thing I like about both these tents is the fly can be setup by itself, like using a tarp shelter or with the tent. Another brand to look at is the Go Lite shelters. The Hilleberg tents are top of the line, but expensive, though you will likely never buy another tent.
If you want just a fly shelter, a plain tarp works pretty good, cheap and light. There are some youtube videos showing different ways to set them up. There seems to be a movement towards tipis as well, with some guys running stoves in them.
For sleeping bags, I've got a Big Agnes Salathe and use a Thermarest Ultra-lite pad underneath. The BA bags don't have insulation on the bottom so you need a good pad, the BA pads are cut to fit the bags specifically. It would be hard to beat the Wiggy's or Feathered Friends bags, but remember that it will likely be damp in NZ even up high and down may not be the best choice. As already stated, the temperature ratings are generally optimistic, buy one rated for colder than you expect. Take into account if you sleep warm or cold as well. The great thing is you have tons of choices when it comes to tents and bags, making a decision is the hard part!