thats the starter relay if i am correct, possible over current has cause wires to heat up and melt them and the casing , usually see this type of thing in my rc car hobby from to much current being pulled, ie a motor jams and draws way to much current for the block to handle hence it melts wires and the connector block. that would be my best guess
Cheers mate that sounds about right as I've just found out my starter bendix had jammed and I was trying to start it so guessing I need a full new wiring loom
Not really a new loom, thats a lotta work to fit. better still is finding a second hand connector of the same type. keep the wires on the new donor plug till you get home then prise out the connector spades. some careful unpicking you should be able to salvage them, cut back your melted wires fit the new spade connectors and stick them into the replacement donor plug ( take photos before hand of the old plug so you know where wires go ) , pop plug onto the starter relay ( i would get a new relay to be very honest ) , check the motors bendix aint sticking or jammed, then cross fingers and give it a turn over, you could be lucky and save yourself a good few quid.
