denman: had a look at all your issues listed, looks to be ok.
Popped out the cycling thermostat and it appears to be working fine, checked by putting it in the oven to heat and it opened, then closed again when cooled. The one thing though, there are another set of wires on this thermostat, purple ones. On the wiring diagram this appear to be the thermostat heater, and it was open both room temp and hot. Could this be the original source of the failure?
To re-iterate, this unit has had a thermal fuse blow twice now. The hi-limit thermostat was replaced after the first failure. Could a failed thermostat heater within the cycling thermostat be the cause of this issue?
Thank you all for your replies!