I have been using
Hosting Bay - The Cheapest Business Hosting Service in Australia for about 7 years for a number of smaller sites.
I never had any real trouble with them, I have done worse with big American hosts.
They have both Australian (servers in Melbourne, I think) and US packages,, but no unlimited Australian ones.
The biggest one here is probably
Web Hosting from WebCentral for Small Businesses, Corporates and Enterprises but they are very expensive and might be too much focused on the very big end of town and government contracts.
Cheers