I couldn't get the plastic panel off the back of the inside of the fridge. I managed to get the other two plastic parts off up the top, one with the thermostat to change the temperature and another bit but, even though I removed the two screws at the top of the panel I still couldn't get it off, there was very little room around it for leverage and it's quite flush with the back of the fridge.
Is there any special knack to it?
The only metallic thing I could see was a small, vertical metal cartridge (like a mini scuba diving tank) about 5 centimetres tall/0.5 cm wide behind a plastic grille which I could raise but would then drop back down with gravity. Presumably not what you meant by the bi-metallic device but thought I'd mention it.
I found the tray for condensate and it had a shallow pool of very dirty, oily water with a heating element in it, like a kettle, presumably to help it evaporate. It is next to the compressor rather than below/above it.
Yes, the fan goes on when I press the door close light switch and off when I release it so the fan's at least working.
Thanks all for your help so far!