UK Car Repair: Vectra B 1997 CDX Estate 2.5V6 Automatic with Electrical Short, fuse blows, mirror adjustment

Question
Hi William - There was I happily motoring home last night when all the internal courtesy lights came on. Accompanying this was an electrical "burning smell". Pulled over and switched off ignition and internal lights remained lit. RAC arrived and checked fuses - both 18 & 20 had blown and in replacing 20 it kept blowing immediately. He was ex Vauxhall man and checked the obvious (to him) but no result. Many electrical systems are out with the exception of main lights, windscreen wipers/washers, heated seats, and electric mirrors - interestingly when operating the electric mirrors the courtesy lights come on again for the duration that you hold the mirror adjustment switch in the on position!!! Car is otherwise in A1 condition and cannot cope with thought of losing it to this. HELP ME PLEASE!!!

Answer
Unfortunately I do not have access to a wiring diagram for your car. It sounds as though the body control unit caused the problem.  Other than taking it to a garage, you have to remove the connections from behind the no 20 fuse, with a new fuse fitted -or a test light-, replace the connections one by one until the fuse blows or the light comes on, that circuit is the problem. Now disconnect that wire and reconnect everything else, check to see what isn't working and get back to me.