There are a couple of companies that advertise in VW Driver mag, but they seem to be very expensive, and when I called them for some advise, most unhelpfull.
I've just fitted a secondhand kit in my car, but am having a minor issue with it, that I think maybe wiring related, and am struggling to find someone that will help me. If you do find someone to do yours, please send them your way.
I would spend the extra £250 and upgrade your radio to the RCD510. There are plenty of "as new" ones on ebay. It will make full use of the phones features all operated very easily from the touch screen, rather than having to scroll through your address book one at a time and dial numbers using the steering wheel buttons on the DIS.