I know there are tons of Australian quilters, so they must be feeding their fabric stashes somehow. Maybe Google "Australian Fabric Shops?" Surely postage would be less expensive within your country. Otherwise, prepare to pay big postage. Especially from the States. The US charges an arm and a leg to ship internationally. It wasn't always like that, but it is now.
Support your local shops. It's good for your economy. Otherwise, look for really good deals and factor in the postage to see if you can afford it. This hobby sure isn't cheap is it?!