The problem with homes is that many of them will insist on being different, so that a 'one size fits all' heating system is not possible.

Correct me if I am wrong, but it sounds like your heat pump is operating in weather compensation mode, but also being controlled by four thermostats. If that is the case then I don't think that your system will be operating at maximum efficiency.

In an ideal World all the thermostats would be set 1C or 2C above the desired temperature, the weather compensation would be adjusted such that the rooms are heated to the desired temperature and correct balancing of the radiators ensures that correct desired temperatures are maintained throughout your home.

Of course we don't live in an ideal World. Bedrooms can be possibly kept cooler by lowering the thermostat or using TRV's. As far as the 'kid's' problem is concerned, have you considered threatening that you will 'sell' one of them to pay the heating bill, if they do not stop leaving the doors open? Obviously don't indicate which one you would 'sell', otherwise the other's may leave the doors open deliberately. 😋 

Whilst auto adaptation should control the temperature in the room within which the temperature sensor is located, it cannot control the temperature in numerous rooms all at the same time. If the selected temperature sensor is located in the living area, it will not prevent other areas of the home from getting warmer unless the cause is also affecting the living area.

Fine tuning of the weather compensation and correct balancing of the radiators is not a 5 minute job, and could take quite some time to achieve.

Very well said, especially the selling of said-child! Fully agree re difference between all of our homes - it's a challenge! Thanks for your help - here's a few further comments. Looking to learn from anyone who can help on here.

Correct me if I am wrong, but it sounds like your heat pump is operating in weather compensation mode, but also being controlled by four thermostats. If that is the case then I don't think that your system will be operating at maximum efficiency.

I have turned off the weather compensation mode and am controlling the flow temperature manually (using the app); I've also disabled the four thermostats, just leaving them open - i.e it's a fully open system with low flow temp water running round the radiators most of the time

In an ideal World all the thermostats would be set 1C or 2C above the desired temperature, the weather compensation would be adjusted such that the rooms are heated to the desired temperature and correct balancing of the radiators ensures that correct desired temperatures are maintained throughout your home.

Fully agreed - I think, the more I think about it, this is essentially what I'm trying to do in a very manual sort of a way. 

Whilst auto adaptation should control the temperature in the room within which the temperature sensor is located, it cannot control the temperature in numerous rooms all at the same time. If the selected temperature sensor is located in the living area, it will not prevent other areas of the home from getting warmer unless the cause is also affecting the living area.

Can I check if I've understood this correctly - so if I went ahead with this new mitsubishi controller - there would be four thermostats, one on each of the four floors, but of course only in one room of each of the rooms on that floor - so the ideal is that the temp set on that new controller, say 19 degrees in the living room, would also apply to the next door room which may only be 18 degrees. So there's still a trial and error in finding the correct setting for that floor. BUT - this could possibly be overcome by balancing of radiators between the rooms on a specific floor given enough time and attention?

AND the second part - is that this auto-adaptation would be superior to the current on/off old fashioned thermostat that is in place? Clearly the heat pump won't supply different flow temp to each of the four floors, so I imagine this isn't the case.

@ecodannewcastle

Correctly adjusted weather compensation will vary the LWT automatically, rather than your present manual adjustment. Let me explain how weather compensation is designed to operate.

The laws of thermodynamics would indicate that the rate of heat energy loss from your home is primarily determined by the temperature difference between the indoor temperature and the outdoor temperature. To maintain a constant indoor temperature it is therefore necessary to replace this heat energy at the same rate as it is being lost. If the heat energy supplied is insufficient then the indoor temperature will start to fall, but as it does so the temperature difference reduces, which in turn reduces the rate at which heat energy is lost. It is all a balancing act.

Weather compensation measures the outside temperature, and using the weather compensation curve calculates the required LWT necessary to maintain the indoor temperature. The weather compensation curve needs to be adjusted to each individual home, and can take some time to achieve, which is probably why many designers and installers are not in favour of using it.

Even correctly optimised weather compensation may not keep the indoor temperature constant, because there are other factors such as solar gain, wind chill, rain effect and even 'children' that the controller cannot take into account when setting the required LWT.

Mitsubishi developed auto adaptation to help get around some of these problems, though it also has its limitations. A temperature sensor, either hard wired or wireless, is placed in the room where the temperature is to be controlled, which will also help control the temperature in the other rooms in the home.

In your situation having four remote controllers I don't think will allow you to control the individual temperature on each floor, since if my understanding is correct it will only control the temperature in the room with the designated remote controller. The master controller will only accept the temperature reading from one of the four remote controllers, though I do believe that the master controller can accept setpoint changes from each remote controller, but responds to the last instruction.

Even with a remote controller and auto adaptation it would still be necessary to balance your radiators to achieve reasonably constant temperatures throughout your home.