Well, a total non-event.

I plugged the AAWireless dongle into the Subaru USB, and buried it in the centre console compartment.

Opened Bluetooth on the phone, paired with the AAWireless.. and after a very short delay my phone connected to the AAWireless WiFi hotspot. Then.. Magic happened. Android Auto popped up on the in-car screen and that was that.

The phone still had full internet access despite the Wifi connection between the phone and AAWireless dongle.

I've now combined that with a 15W Iniu wireless charging pad in the car and all good.