First thing I looked for, is does the boiler modulate and the manual shows
View attachment 321181
so output between 14.28 and 28.30 kW, and it refers to a latent heat collector, so it does seem to be a condensating boiler. So the main control is the thermostatic radiator valve, (TRV) basic idea is, hot water is pumped to radiators, these warm the room, and cause a air flow within the room, when the return air heats the TRV it closes, not simply open/closed but gradually regulates the flow, as the pressure raises the by pass valve opens, allow hot water directly back to boiler, so the return water gets hotter, and the boiler senses this and reduces output, once the output can't be reduced any more, then the boiler starts to cycle off/on, so we fit a wall thermostat to switch off the boiler when the cycling gets too much, but room temperature is controlled by the TRV not the wall thermostat.
The problem is the TRV takes time to open and close, so the flow needs restricting with a lock shield valve to give the TRV the time it needs to adjust. So the user is left with two adjustments and nothing to tell them which to adjust, and a TRV with *123456 does not really help, one wants some thing like 20ºC, so by moving from mechanical to electronic you get the temperture displayed as 20ºC. So direct
View attachment 321184or with an app
View attachment 321185 you can see what is going on, and with the app you can see target and current, and in cold weather current should never exceed target, if it does the lock shield needs closing a little, so it also helps set the lock shield valve.
Fitting is by one screw ring, no wiring up, cost does vary £15 to £80 depending on what features, so can link to a hub/wall thermostat to tell the boiler when to switch off/on, and I moved one electronic radiator to radiator to set lock shield valves, once set the old mechanical worked A1 if you always want room at same temperature. But you can also set time and some do connect to internet so can be remotely controlled or use geofencing. And no wiring required, and they help the boiler extract the latent heat.
I fitted in mothers house with idea of fitting a wall thermostat latter, but once set worked that well never bothered with new wall thermostat.