Thank you very much for the information. I was going to register but haven't yet done so. Tomorrow will be a good day to start the process.
Years ago I was registered and used to buy both physical and certificates but gave up buying certificates and found it was just as easy, or easier, to buy from Ainslie Bullion here in Brisbane. Their prices are more than competitive. (just for background information - not a 'plug' for Ainslie - but they are also much easier to deal with)
In order to get stock remaining details it appears I will have to go through the long, drawn out process of registering with The Perth Mint. What a striking contrast to how simple it was when silver was $7 USD per ounce and buying silver through the Perth Mint involved one phone call, getting an order number and transferring dollars or sending a cheque.