In search for a solution to get music going in the car, I looked for an Aux-In possibility. I made the harness but the Aux switch didn't work. VW won't take it back without "booking the car into the workshop Sir" (avoid Leeds VW).
Anyway, I decided to see if I could turn the iPod dock in the armrest into the aux in. It's very, very easy to do and works just like the aux in switch.
1) Remove the iPod dock from armrest (just pulls out, no screws)
2) Cut wire 8 on the iPod dock side (NOT the harness coming from the armrest). You can also remove pin 8 on the iPod dock. This is more work but it will make this reversible.
3) Code Aux-In using VCDS (you must have an RCD300/500 with silver buttons, it will not work with older units). Change the last digit from a 2 to a 1.
4) Plug in a 30pin to aux connector
5) Voila, free aux in. The harness I was building cost around £30, so this is a nice free way to make use of the outdated iPod dock.
Enjoy!