Just joined this fantastic forum to post my results:
I sourced a GD-03 unit from Ebay for about $300 and followed VTHs guide to install. As a lot of people have found, the usb/cable is a bigger issue than installing the unit itself!!
There is a quick workaround though - the cable Teegan linked to on Aliexpress does work. It's also available on ebay sellers with Australian stock for about $16. There are two versions so buy the one that terminates with the usb port.
Then, just plug the cable I to the back of the head unit and run the usb end down the back of the a/c unit and out the bottom of the fascia (near the glovebox) and that's it!!
The only parts that needed to be removed were the air vent trims and 4x screws holding in the head unit
Firstly, thanks to everyone who has contributed to this very helpful thread across the years. My 16yo daughter just bought a 2015 Active-X for her first car, so this thread continues to give in 2024!
Anyway, I have a cable like the AliExpress one mentioned - plugs straight into the back of the GD-03 unit, with a female USB plug on the other end. After initially installing, it seems to recognize the phone (iPhone 13) very briefly, but not connecting for CarPlay. Does the existing USB/aux need to be disconnected for this method to work? Have tried a couple of lightening cables, including one we're sure is genuine Apple to no avail. About to update firmware. Beyond that...?
Edit: updated the firmware and CarPlay worked briefly, but now getting the "iphone is not responding" message. Anyone else have this and able to suggest the solution?