Alright, here it is... the adapted aux adapter cable. There are at least two long threads on this subject already, but at the request of perl, here's the condensed version of how to make a cable from scratch that doesn't need the CD Changer cable to be removed or cut. Thanks of course to the many people who've helped pull this info together over the past months. I hope this moves us all forward - don't wait for MINI..!
This will work on 2003's and will allow you to charge and play from an MP3 player at the same time.
You will need a pair of coupling transformers (p/n 141621), a pair of 6 way connectors (p/n 103211 - it seems they don't stock the 12 way anymore) and the pins to go in them. You'll also need the crimp tool and jaws to suit these pins - I don't have that number as we already had all that kind of kit at work. You'll also need shielded stereo wire and the end connector of your choice (either plug or socket).
Here's the circuit you need to build
And here's where it plugs in
As always this is for information only - YMMV.