I have a Mk-IV, 16:9 colour nav system, and I had no radio split when I bought the car. In spite of a picture in the nav system manual of o 16:9 screen showing radio split, still the dealer would only show ignorance and insist that it was not possible, not an option, not necessarily available for my car ... I finally sorted it out following instructions found in this same web:

http://www.xoutpost.com/articles/x5/n...s-upgrade.html

I don’t know if these may work for a Mk-III. Given your recent experience, I would suggest you don't mess around downgrading and upgrading, but follow KiwiJochen advice and use his NavCoder application to set your type of radio, if you have access to your iBus.