How does a thermostat on a British hot water urn work?

Are they different from smaller American coffee makers? (They have
big coffee percolators in the US too, for public meetings and large
parties, but I've never taken one apart, and I don't know if they are
the same as in England anyhow.)

Someone from England writes:
The type of switch I was discussing has the bi-metal inside the switch unit,
not on the surface of the water container, therefore it is not a passive
device soaking up the heat of the water. ....Push enough current through a bi-metal strip
and the strip heats up and breaks it's own circuit. The amount of current
flowing though the bi-metal strip can be regulated by a variable resistor
attached to a dial.

Does this sound accurate?

This strikes me as using a bimetal strip just to make a timer. Am I
right and have you ever heard of such a thing? If one is not using
electronics, how is an interval timer for a high current device like a
water urn made?

Would it be done by running current *through* the strip, as it says
above?

These urns, and coffee pots in the US do have a method for keeping the
water at the same temperature, when the red light is on, hot but not
boiling, and the particular urn being described has iiuc two modes,
one that uses an interval timer, and one that does measure the
temperature.

Does anyone know about this from a British pov?