A while back there was a thread somewhere that had folks talking about raised garden beds.
I mentioned about the galvanised corrie iron ones and also the colour bond raised beds as well. these are along the lines of water tank shapes and are instant
Now here in WA they are available from http://gardenersdirect.com.au/
I have since found a couple of others for those of you on the east coast.
http://www.birdiesgardenproducts.com.au/main/
and
http://www.patonsheetmetal.com.au/garden/index.html
hope this helps someone