Thought I should share this useful info. I had a Kenwood KDC-B7021 head unit that wasn't working.

Its a unit that has a pivoting head unit and the ribbon from the head unit to the main unit had split (though this wasn't obvious to the naked eye, only when it was taken apart). A couple of repair centre's offered to do the required repair for £70, but if you can use a screwdriver and are confident enough to push a connector into a slot then you can do all the work in under an hour yourself.

The ribbon connector part can be found on ebay for about £15 (might be cheaper from the Kenwood parts centre) and its very simple to take apart the unit and replace. PM me if you want more details.