S3 2008 Won't Start

Or dodgy wires on the back, could've had a rough time under seat, too easy to cram things under there.

 

OK, that rules out that particular line of thought. But, check the female side anyway especially, as someone else pointed out, the wiring. It could easily be co-incidental that the problems (seem to have) started after plugging in the diagnosti but you have to eliminate the socket as a potential source anyway - unless it doesn't carry any live feed?

 

It does carry a live feed Adie , basically comes from the 5a fuse which keeps blowing

 

Ah, so .... definitely worth checking continuity of each of the plug's sockets, then.