I had the same problem after reading this post, the head unit would on say 'No CD' and nothing about AUX input even with my iPhone plugged in, i went to VW and asked them if they knew why it wasn't working, someone had a play around with it and then decided to give up. (They then told me it would be £50 to send my head unit off to get fixed) I then went to motor mania in burton and they advised me to go to Phly Audio Services and in there words 'He seems to be able to sort everything' I booked a appointment with him, as soon as i met him he pulled out his computer plugged it in to my diagnostics slot and 5 mins later he said 'it was 1 number that needed changing to make the aux connection work, all the wiring was there VW has obviously programmed it wrong' ever since they it has worked perfectly.