Harry Bloomfield wrote
Rod Speed wrote

Yes, but you will find if you measure it properly that the heated thermostat does produce less difference between the
highs and lows in the room.

As you said, it just doesn't work as designed - it's guessing!

Nope. Its trivial to prove that it does reduce the dead zone/hysteresis.

All that happens is when the heating is needed to be on more, it thinks it's going to be warmer than it is, so it
doesn't switch it on enough.

Fraid not. If that was the case, you would see a bigger swing in the room temps and you dont in fact see that.

Out of nothing more than curiosity, I have checked back through my
house temperature logs. I don't make any particular point of storing
the logs,my system just stores weather data and along with that data, the house's temperature and humidity - every 5
minutes.

At the moment we are running on an electronic wireless thermostat.
Aside from times when an outside door has been open for a while, the room temperature is held within 0.6 deg. C for
the entire day.

Looking back through my log to a little over two years ago, when we
had a wired electro-mechanical stat., in the same circumstances, the
temperature appeared to remain within 0.8 deg C.

You should see the biggest difference with the lowest outside temps.

And you dont have the figures for a bi metallic thermostat with no heater.

If you did, it would have a higher range again.