In reply to lordlamberino: Bring your climbing gear with you, because buying in NZ is more expensive than the UK for a variety of reasons (NZ's isolation, costs of transport, smaller markets for kit, etc). There are options for purchasing from the US, but the NZ postal service and customs are increasingly looking to levy GST on more expensive purchases.
Make sure it's clean. The shipping manifest will identify the contents of each of your packing cartons, so that customs can identify which cartons to check. Tents, boots and sporting equipment are of interest to customs for obvious reasons.
I didn't have any problems with any of my stuff (ropes, climbing hardwear, and mountain bikes). Remember that your shipping will pass through the tropics and you might wish to think about whether you use plastic bags to pack clothes and kit inside the cartons (there are considerations about condensation).
You'll need shipping insurance (shop around) and funds to release your shipping from customs in NZ (possibly storage too, depends on whether you have an address sorted for delivery).
Final thoughts:
There isn't/wasn't a customs levy on importing personal possessions for the first time shipment that a migrant imports into NZ, although I'm not sure if that applies for subsequent occasions. I know friends who have thought afterwards that they should have brought more of their outdoor stuff from the UK when they first arrived, as they had a shock at the prices when they began purchasing in NZ. 'Trade Me' is a NZ way of life to pick up outdoor stuff more cheaply (but be surprised for the costs of some pre-loved stuff).
Shipping back to the UK is far more expensive than shipping to NZ, as many returnees to the UK will admit. Not a pleasant thing to consider, but if it doesn't work out for you, will there be items that you can't face being separated from?
Good luck and enjoy your new life in NZ!