I would think that 13 Amp mains Flex would do the job, the number would be their part number, nothing else, get some crimp terminals fitted as needed. They will be then tight fit.
Question is WHY did it melt, Has it melted fully, or just insulation? loose connections would melt insulation off, so as above, but to melt fully, Takes a LOT more. If you have a test meter, check out the heater element. And check your fuse box, If old style fuses, check fuse wire in them is of correct size, Something like that should of blown a fuse or trip.
SD, January 2012