See picture - right side of the photo is the front.
There's two resettable thermostats: one at the back and one at the front. There's also what I assume is a non-resettable thermostat at the front.
It's the resettable one at the front which keeps popping.
Is what I think is the non-resettable thermostat the cycling stat..? Is there any way of testing a cycling stat - i'm not quite clear on it's purpose in life. Are you suggesting the cycling stat is responsible for maintaining a reasonable temperatue and that it might be indicating, all the time, that there isn't enough heat and the resettable thermostat trips because the cycling stat isn't doing it's job..?
If I look very carefully at the picture it looks like the resettable thermostat at the back and the non-resettable stat at the front are wired in series. Does that make any sense..? The front resettable thermostat looks like it controls power to both elements.
I could do with a wiring diagram for this beast...
[ I take pictures of everything before I start any job so I can figure out where all the left over bits go..