I live in Australia and now have the hearing aid feature. I had to go to NZ to get it set up. Can I tell you just how amazing it is. I have mild hearing lost according to Apple. This device has changed my life. All the sounds are crisp and clear. My god. Wait till you try it. When I
take them off the World goes quiet. Amazing product. Note that once I downloaded the NZ software it took about three hours for the product to automatically register. It now just pops up when I put the Airpod Pro 2 on. I tell you it’s worth the wait.
I hope you have switched the IOS Auto Update off your iPhone. If Apple push a new update to your iPhone in Australia you will lose the hearing aid feature.
I have been using my AirPods Po 2s in the UK as hearing aids since September running IOS 17.7.1, (the hearing aid feature has been available since September 2022). With Auto update off the reminder to update to 18.1 or newer was constant for the first couple of weeks but the notifications finally disappeared before Christmas.