Okay, so It seems I may be able to fit the US style tow hitch with the UK wiring (thanks for all the help, on this and other threads). After searching through the US versions of BMW, Amazon and Ebay it seems all the BMW X3 hitches are listed as 2005 - 2010, but this must be a mistake?
e.g.
Amazon.com: BMW Trailer Hitch Kit-Class 2 Trailer Hitch - Class 2 - X3 SAV 2005-2010: Automotive
On realoem it lists the same part number for the Dec 04 X3 3.0i, Dec 05 X3 3.0i and Dec 06 X3 3.0i So...does anyone know will the one listed above fit my Dec 04 2.0d?