To cut a long story short, the stereo only stays on with the ignition on. With the key in the auxilliary position, the stereo turns off after 10 seconds or so, and turn on again briefly if you open the door, operate a window, etc.

Anyone else had this, and found a resolution?

Could this behaviour be altered with VCDS?

(Otherwise, I'll be looking for an ignition switched fuse connection to patch into the stereo and disconnect the can-bus switched feed.)

Cheers for any help and guidance.

In the wiring loom for the after market hu there might be a yellow connector with a bullet plug on it if there is there should be a spare connector you are able to swap the connector into from where it is now try that

An update - I called Connects2, who make the wiring interface. I was told that this is a known issue, however, there are no plans to write new firmware at the moment.

A local audio dealer, Car Audio Security, confirm that this is a problem with some VAG vehicles, including symtoms such as being unable to turn the radio off.

Not good, but at least I can live with having to leave the ignition on if I want the radio on.