I have a combi boiler here at home. When I moved in, there was no thermostat at all, just the TRV's.
I installed an electronic programmable thermostat from Maplin the first year, but as I have posted elsewhere, I am still not happy with it. The problem is that my house is now so well insulated that it continues to get warmer even when the thermostat has shut off.
This guy has the same trouble with an electronic thermostat he just bought from Amazon:
Now, the old mechanical thermostats used to have what was called an 'accelerating resistor' inside them. This provided a small amount of heat inside the thermostat when the boiler was running. This reduced the hysteresis, (the difference between the on and off temperature) and so reduced the effect that I have a problem with.
I will have to chase out the wall to fit a back box to install a mechanical stat, which would make it difficult to go back to the electronic one. Does anyone think it worthwhile?