I decided to fit a Dension Gateway to my car so that I could more easily integrate my iPhone with the BMW's iDrive entertainment and telephony system. Since my car already had CD changer prep, the wiring was already in place to connect this up.
I spent a lot of time trying to code the BMW computer to recognise this unit but with no success. I ended up taking the car to a BMW specialist with Autologic diagnostics equipment who was able to successfully code the car for me. Thanks to Andy at Ayrshire BMW Specialists.