Hi Guys Well I tried cleaning the fuse board earlier as there was some corrosion. I did find the horn connector had snapped to as a temporary fix until my new fuse board comes was to add a small amount of solder to the broken tang and I wished I hadn't. I plugged it all back in and turned the ignition on and smoke came out of the fuse box and burnt through one of the earth leads that goes to White Connector D22 and burnt out the track in the fuse board. Now I'm not sure if this was my soldering or the fact I used contact cleaning fluid to clean all the plug sockets. So I'm further back from square one now. Sometimes you wish you left things alone but then I'd never had found the horn issue. Please see the pictures attached and any advice would be most welcome before I put the new fuse board in. Also what is the size of the earth cable that goes in that socket? It's thicker than most earth cables. That earth goes into a 4 way earth block. The other earths are 1mm cable. I've just found that earth cable in the Haynes manual and it's 1.5mm and the block it connects to is part of the earthing for the Fuel Pump which I've not touched. I think I possibly got some contact fluid in the fuse board somehow and caused a short. https://flic.kr/s/aHBqjAqAbU
New fusebox slaved in today and normality has resumed. That will teach me to tinker... Also replaced the damaged earth cable.