A link here for the A'Van A Shaped camper trailer club of Australia;

http://www.avanclubaust.org.au/

Although this club is for A shaped camper trailers only, there is another group on the NSW coast that takes all types of A'Vans in its club;

http://www.sccavanners.com/

There may be other A'Van specific clubs for all types but I don't know of any. Many A'Van owners of all types just join a generic caravan club if they wish to join a club, that way it doesn't matter what they've got.