I've been through a couple of  ebay 'item not as described cases' so I know your in a hard place.  Ebay policy is to side with the buyer unless there is a track record of the buyer making many such claims. My thinking is when an Ebay CSR rep looks a case they look by account name. Previous claims wouldn't show as the serial INAD'er is clever and has a different account for each claim.  A seach by street address would bring up a full record.  

I think your best bet is Australia Post. They take an extremely dim view of people using their service for anything other than to get mail delivered.