Update 6:
Decided to do a relatively minor mod to the Send and Return sockets in the Diecast box on the end of the FX Loop breakout cable, this basically involved soldering a 2M2 resistor from each socket's tip connection to circuit-ground, this was done to stop loud popping-noises coming through the amp due to a couple of coupling-caps in the FX Loop circuitry, one end of the caps was tied directly to the tip contact of their respective socket, this provided no path for built-up charges on the caps to leak to ground, adding the two 2M2 resistors now provides the path to ground without a detrimental effect on the signals in the FX Loop, I've tested it out and it is still working perfectly.
