There is an excellent article on the Alpha Flying Group in this months's "Australian Flying". It costs $2500 to buy a share which you can sell when you leave.
Their members own an Archer, a C206 and a Saratoga, all IFR with TSOd Garmin 530 GPSs, autopilot coupled.
They are based at Basair (Bankstown) and their web site is worth a look at -
www.alphaflying.asn.com.
As for availability, members have told me it is not a problem and this can be shown by going to Basair and having a look at their forward booking sheet.