Ideally you should have 1/4,3/8, and 1/2 inch drive sizes ( Is that what you guys call the various drive sizes down there?) rated in (1/4 and 3/8)inch/pound and (3/8 and 1/2)foot/pound or in metric kc/cm or Nm respectively. Realistically, you should be able to do most anything to your bike with 1/4 and 3/8 drives just look at the torque range spec for the wrench. I'd recommend a look at the torque specs listed in the tech vault to get an idea of what sort of range you'll need. Don't buy the cheapest you can find but there's no need to break the bank either. I'm not familiar with Aussie tool brands or I'd recommend something more specific.
I have 1/4 and 3/8 beam type in/lb, kg/cm. They are old Honda dealer service tools, 30 + years old and S&K 3/8 and 1/2 micrometer style in ft/lbs, Nm.
Here a link to torque unit conversions. Handy info.
http://www.vcoa.org/700-900-faq/ImagesSpecialTools/TorqueSpecs.htm
