My boyfriend and I (both big Amiga enthusiasts) are about an hour or so South of Brisbane. Maybe if we found a few others, a Brisbane or Gold Coast club or something might be viable. Actually, if people were willing to travel down to the bottom of the Gold Coast, we have access to a good ex-Scouts hall that would be perfect for a club or convention, it's got male and female toilets and shower, a big kitchen, a main hall and a good size park area outside with BBQs. I'm pretty sure it's only $50 per day to rent the place too, so that wouldn't be too hard to cover.
By the way, for any Australians who don't already know about it, we've got a group on EAB called "Australian Amiga Users" here - http://eab.abime.net/group.php?groupid=4
I guess it's just a way of keeping count of how many of us are on here, but I think it's worth joining.