im guessing this was my fault for either overloading the Sata cable or when I installed a PCI-E Riser the wrong way around in a pcie 16 slot. Was pulling my mining rig apart and found that a data cable was stuck so pulled a bit harder and the plastic came off the psu. I then noticed that a couple of wires had melted. Continued to use it for a day or two without issues however have now got a spare. Question is can I continue to use this psu (apart from the one offending sata port), if I can am I best to put a sata cable on there just to keep some separation between the points? Or could I use the psu but without any of the sata/perif ie using the vga and motherboard connector only. Or is it best just to put it down to a life lesson and bin it

Should still be able to use it. You just won't be able to use that one port.

RMA it or buy a Bigger Power Supply.
Do not take the chance of burning down your home and maybe other homes as well while you are running for extended periods..