Not an Australian product, but definitely a lovely alternative to the indonesian woods. Worth a look, http://www.hardwood.com.au/media/roasted-decking/roasted-decking-brochure.pdf

Hi I would check that your deck can take extra weight like tiles and additional cement sheet products as well. It looks to me like a light timber frame structure but it does have steel beams holding the cantilevered weight. I would get a designer or draughtsperson to look at it and give you some ideas. If you use a hardwood it will grey off naturally but you will have no maintenance. If you stain the timber the maintenance is every 2yrs really...

our obsession with antibacterial products apparently is creating bacteria which are resistant to antibiotics. They should be banned if the government could take any decisive action (not talking about general disinfectant here, just every surface spray for the kitchen and hand washing that also "needs" antibacterial)......

I've coated many decks and the best advise I've been given is "leave it natural". Most timbers go grey after a few months and don't look too bad. If you want a bi-annual maintenance job the other bit of good advise I've had directly from the manufacturer is put down four coats minimum. The third and fourth coats won't use so much oil because they don't soak in. A very light sand between coats keeping in the direction of the grain is a good idea to retain a finish without wood grain or dust spoiling the final appearance. Two coats, no matter which brand or type of oil will last about a year in our sun.