Have a look at CASA (Australian CAA)'s website on
www.casa.gov.au
It has a good explanation of the procedures for getting a Validation/Special Licence. It's quite straightforward and inexpensive.
For hiring a plane, the flying club will probably want to check you out. Not necessarily a lengthy checkout though. By the way aircraft hire works out at around AUD 1 =GBP 1, so it would work out quite cheap considering the current exchange rate of around GBP1 = AUD 2.75.
Birdy