Hi Rob
If its just a few small parts I get mine from BJs here in Brissy but for major parts I buy from England at RGM, or Butons British Bikes, only take a few days for the parts to arrive (quicker than Aust Post) and a lot cheaper in the long run, parts in Australia are so over priced, I brought a new seat for my bike from Burtons British Bike Bits from England and with shipping to Aus I still saved $150 from what I could get it from here and it was at my front door with less than 3 working days, it pays to shop around and save big time, I hate being ripped off, but there are some good suppliers in Australia as well, but with the high Aussie $$$ at the moment you will save so much money buying overseas, thats the good thing about the internet you get to see what the price of parts are realy worth, but knowing what you can get for the price overseas can also work in your favour here by haggerling the prices down from your local supplier, but some are just too greedy.
Hope this helps you to decide.
Ashley