After our little wiring issue on the way to the Plough for the RBRR, I decided to investigate a tad further. After removing both of the dashboard clocks I was able to get to the part of the loom that had got hot and melted.
After the laborious task of removing the loom tape and separating the offending wire from the pack, I was able to see that the damage was contained to a two inch long strip and had not burnt through or melted any other wires.
This section of wire was cut out and replaced with new making sure that all connections were good and tight. I then decided to investigate the fuse box as really, the fuse should have blown before this wire had a chance to melt. Removal of the fuse showed it to be a severely scorched, but not blown 35 amp fuse! I have never seen a fuse that was so badly burnt, but not blown.
Then I remembered Doug and I had an wiring issue when we did the Chinese rally in Holland in March and had been putting in fuses every 50 miles or so just to get home. In the end we had run out of the correct fuses and were having to put anything in. Obviously this was still in there from then. That will teach me to forget to replace the fuse for the correct one at the time!