I'm not a Kiwi, but I may be able to help address some of your concerns.
I'm not sure what "trademe" is, though, so I can't guarantee my response will be entirely applicable. I tried visiting both "trademe.com" and "trademe.nz" -- the latter isn't a valid URL, and the former just looks like a parked domain with a couple of links on it.
But one thing I wanted to bring up is an issue I hear quite a bit from new online sellers, mostly those located outside the U.S. There seems to be a misconception that you as an online retailer are limited to selling products to buyers within your own country, and must therefore worry about shipping cost and time from the dropshipper's location to yours.
This is absolutely untrue -- it's completely unnecessary for you to limit yourself to marketing products to buyers in New Zealand. Instead, you can market your products to buyers located anywhere your dropshipper(s) will ship, and to minimize shipping cost and time, you can market products from your NZ dropshippers to NZ buyers, and products from your Aussie dropshippers to Aussie buyers, etc.
I personally dropship my products to most countries around the world, since my primary dropshipper will ship the products worldwide. It makes no difference that both my dropshipper and I are located in the U.S.
I hope that helps!