If the plan to buy in the UK and ship to Oz fails, have you looked at US sources? One seller on eBay US
http://www.ebay.com/itm/KING-DICK-UK...98b5c3&vxp=mtr has a variety of Whitworth / British tools. They also have a web site
http://www.britishfasteners.com/ with even more choice. I don't have any experience to be able to advise either for or against. I didn't see a clear statement on shipping outside the US on the site.