Wiring options for replacement wired thermostat

Hi,

I have an old tatty Eberle thermostat that I never use. It's connected to the plinth heater in the kitchen. It would be nice to replace with something newer, but I'm not sure about the logic with the current wiring. It seems to be 3 phase without neutral so red, blue, yellow and earth. Below are is an image of the current wiring and the wiring diagram on the back of the cover...



Does this wiring seem correct as is, and can I only replace like for like or a different type of thermostat?

Any advice much appreciated, thanks

Colours mean nothing, you likely have line in, line out, and neutral, however the old switches did not need neutral and some times it is simply not connected, so step one is put the meter on it and check there is a neutral.

Actually looking at the wiring to the fuse and switch on the grid plate i think you're right. red = line in, yellow = line out and blue is neutral. But I will check at some point as you suggest with a meter.

Just because there are three different coloured wires does, in no way, make it three phase!
It is regular a domestic single phase supply.