Thanks for the comprehensive replies. I have stripped the loom off the bike and removed the outer sheathing (a mixture of electrical tape, self amalgamating tape and the non adhesive wrapping) The only wires that appeared damaged was the Brown/Blue wire at the battery-ve and the same wire at the ammeter. This wire does not appear damaged/melted throughout the rest of the loom. The Brown and white wire into the ammeter is also melted with no other signs of damage. There is some small area of damage within the headlight shell, but these were collateral damage caused by the melting wires sticking to them.
I cannot find any obvious signs of a dead short i.e No signs of arcing anywhere. I removed the handlebar switches and again no sign of arcing. I can only believe that when I was pulling at the switchgear wiring I have pulled some wire over to a point where the uninsulated parts have come into contact.
It is definitely not a standard loom as there are a number of wires within the loom that are not connected up and there are a few red/white wires that I cannot find in the wiring diagrams I have.
The bike does not have the PRS8 Switch fitted
My apologies to all, but my level of experience of electrics is very limited and I have no experience of making up a loom, so please bear that in mind when I am constantly asking for advice