Update - I took out the glovebox yesterday - not too difficult once you've done it, but getting it back in took me well over an hour. Unnecessary as the lead I was looking for was just on top of the glove box, so I only needed to unscrew the glove box screws rather than removing all the trim to actually take it out. Will get hold of the 1365708 cable/socket that previous threads have mentioned, and see if it works.