Hi Mick, no issues at all I upgraded from a Chorus 1 din, so I had to change the whole centre console. So I needed quite a few adaptor cables, but the radio just worked just fine.
I seem to remember having to programme it to not have Bose, but that wouldn't affect just the radio. I also had to change the amps when I added the TV tuner, but again no issues with radio.
If the radio works with the old Symphony unit then yes sounds like not the cables, only thing left then is the coding, I have attached my coding spreadsheet which you can compare with your, maybe you will spot a difference....
AUDI_CODES_via_VGA-COM.xls