I used these for my rental this weekend - saved $30
http://www.jetstar.com.au/travelSvcs/carRental/
"Rent a Group X (e.g. Hyundai Getz) in Australia, for a minimum 3 days between the 1st August and the 30th September 2004. You can drive away for as little as $35 a day^^ including GST and unlimited kilometres in metropolitan areas. (200km free per day in country areas and 100km free per day in remote areas. Excess kilometres are charged at 27.5c per km). Please quote rate code 14. "
And also "Avis is offering customers who rent before 31 August 2004 a free one class upgrade to a maximum Group E (Holden Commodore). Simply book through this site and request your free upgrade on arrival at the airport. Upgrades are subject to availability – see full terms and conditions. " which is AWD - P469101
Also, I got the chance to talk to Avis on the phone today and was talking to a girl there who was overly helpful. I had a code that was only for US/Canada rentals, and she had a look and said "Oh, that's cheap. Hang on I'll match that with one for Australia" and matched it. Not sure if that's legal/common practice, but she knew what codes were out there and was able to see what the codes were I was using.