Right I've worked out what the code '1D7 Trailer Hitch Preparation' means (you might have this on the sticker in the boot/service manual with all your vehicle option codes). It is (as people have guessed previously) all the trailer wiring to a plug in the boot (left hand side behind the panel). Here's some photo's: http://www.flickr.com/photos/8753947@N06/with/6971837758/ (top four photo's) There is a red plug behind the fabric panel in the boot, left side. It's covered in a grey foam