Nearly Lost it!

I needed to fit a cigar lighter in the 110 for a sat nav so in the bunch of wires on the dash tray was a purple one which Haynes said was for a radio. Tried it with a tester and it was ign on live, great i thought, easy job, and wired in the lighter, turned the ign on and..........clouds of smoke started to bellow from behind the dash I then had to remove the steering wheel, and all the dash to find and replace the melted wire. It was a white with orange tracer which came from a big clump of white wires. Ive no idea why this melted but i managed to replace it and the one next to it. Spent yesterday putting it all back together, but i now have no Horn( could be the stress of it all) What a weekend! I did notice that the two large terminals on the ign. switch showd signs of overheating as the insulation on the spade ends had melted. Any Ideas?
To cap it all, i tried to jump start my wifes clio with a knackerd auto box and shorted it to the bodywork. Something blew and i now have a clio stuck in park and dead as a doornail.:doh:

all white wires are ignitiion lives ,you must have shorted to earth an ignition live ,wired up cigarette socket correctly?

Seems ok now but still no horn. The loom is a mish mash of different coloured wires and scotch locks and a second hand fuse box from god only knows what vehicle. Still a bit concerned about the ign switch terminals? Could the switch be playing up? Also I was always told not to leave the ign on in a petrol engined car as the coil would burn out, are there any problems doing this in a diesel so i can have radio on?

they are somewhat heated as thats were ignition live wires get there power from ,switch may well be okay ,just need to test it functions forrectly ,like brown wires which are battery lives white wires link together so a short on one ignition side can effect another ,true coil shouldnt e left energised ,but wont hurt a diesel ,often a good idea to give radio .battery feed (brown wire )

Thanks again James, dont suppose you and yours fancy a busmans holiday to the west of Ireland?

would it be a busmans holiday,bet its real pretty country over there