I finally got around to getting the lid off the device and finding the heat source and the only hot part was the device under the heatsink, which I assume is the processor, I've been a little busy so I didn't get it done as soon as I hoped.
(All those that bet that I put my finger on the HV side of the AC - DC convertor, you lost, I'm still here!)
I think I'll try cleaning and replacing the thermal paste, I assume there's a guide to removing the heatsink on this site somewhere, if that doesn't solve the problem, my only other theory is a regulator fault, as running processors at higher voltages will cause them to consume more power.