Older 'dumb' TRVs e.g. https://www.victorianplumbing.co.uk/white-thermostatic-radiator-valve-15mm-angled-trv? are quite easy to fit and may suit? e.g. if in bedrooms, turn up when you/the kids get home, turn down when going to bed. 

Yep I have those on all radiators and try and adjust when I remember.  Probably best to be disciplined and do some adjustments throughout the day rather than spend £45 per valve on a smart one. 

Update.

Thermostat has been set to 16c overnight and 18c between 6am and 7pm for the past few days.

To be honest apart from the initial bit of a boost to get that starting temperature from around 17.2c up to 18c (and more importantly heating the towel rail) the heating is not really firing up. The radiators are still largely cold, energy usage remains impressively low.

20 hours' worth here, the thermostat being set to 16.5 most of the time (14 when I'm out).

As for temperatures, the plumbers set my boiler to 80 for heating and 60 for hot water, they said less than 60 gives the risk of legionnaire's.

(Looks like the HSE agrees. Setting it to 50 as some have done may not be the best idea!)

"Hot water should be stored at 60 °C at least in order to kill legionella bacteria. "

"Outgoing water should be at least 60 °C "

https://www.hse.gov.uk/legionnaires/things-to-consider.htm

Think it is fine on a Combo boiler like mine as there is no water storage and the water is continually flushed through the boiler. Goes from say ,12c out of cold tap through the boiler straight to 50c and then is used.

It was a mistake looking them up to provide a link. My screen is now infested with ads for them -and not just TWO!

22.6. In the lounge this morning with the sunshine through the windows.

With my ASHP and underfloor heating it is actually more efficient, I am told, to leave the heating on constantly in winter rather than making it turn on and off and heat up the slab.

The flow temperature for the floor heating varies depending on the outside temperature, up to a maximum of 50C in very cold weather, but generally should be in the 40-45C range which makes it pretty efficient.

Of course all this is hypothetical at the moment as it is still not working properly (awaiting an engineer who should have arrived this afternoon!). Having said that, when it has been running, our energy usage seems to be much lower than it was with the old heating system. In winter we would typically be using 50-60 units per day which would be somewhere like £20 a day at today's prices. I would hope we can cut that by more than half with the heat pump.

I'm always dubious about the idea that leaving heating on constantly is more economical (which may be different from efficient) than letting the temperature cycle up and down. Newton's Law of Cooling* states that the rate of heat loss from an object is proportional to the difference in temperature between the object and its surroundings. So if you keep your house permanently at a higher temp, you will be spending more energy heating your surroundings than if the house is cooler at intervals. 

Your situation is complicated by the large thermal inertia of the slab. If you let that cool down, it will certainly take some time before you can use energy put into it to heat the rest of the house. So in that sense it may be more efficient, but I think the economy argument holds good overall.

I also dispute the effectiveness of leaving the oven door open after cooking to heat the rest of the house. The residue of heat residing in a hot oven is going to leak out into your house eventually. Leaving the door open just means that you get the heat out of it more quickly, and at a higher temperature. So, yes, an instant boost, which may be what you want, but no difference in the long run.

Better to capitalise on a nice sunny day, like today, which has raised the temp of my living room from 17.1C this morning to 20.6 now.

* an empirical law which applies at 'normal' temps where convection and conduction are dominant - Newton didn't have any extra-high temp sources so he wasn't able to experiment with radiative heat loss.

No need to keep it at 60 all the time though, that is much hotter than you need it. You just run a disinfection cycle.

The heat pump runs a legionnaires cycle once a week to boost the temperature up to 60-65C. Or it would do if it was working as it was supposed to!

PS @DEW that makes sense about a warmer house losing more heat, but apparently heat pumps are much more efficient if they can run at a low temperature for longer periods, rather than having to run at a higher temperature for shorter periods.

Eg if I set the leaving water temperature to 38C I could in theory get a COP of 5 or more (5 times more energy out than in) if the weather is relatively mild, but with the lower water temperature it would take a long time to heat the floor up. Whereas if I let the slab cool down then in order to get the temperature up I might need the water to be closer to 50C, which could cut the COP down to 3 or less.

Maybe once it is all working properly I will experiment with different approaches and see what works best in terms of comfort and cost.

(my mid terrace faces east-west so gets no solar warming at all in winter.  The advantage is that I've not had temps indoors of 21c+ for weeks now,    

Currently a quite pleasant (asuming you are not a reptilian nudist) 16.8c*


* obviously no heating on 

Is anyone going to be in a position to claim that temps are higher outside than in, given the ultra-mild forecast this weekend? I once lived in a student house where there was minimal heating, and on one memorable occasion, there was condensation on the outside of the windows.

I think it may be possible here today or tomorrow given the hours of insolation etc.

23.0c in the lounge. The thermostat just shut off allowing it to drop.

We have had condensation on the outside of our windows several days since we moved back in to our house with no heating at the start of October.

Essan will. 

That's common if you have new windows. I've seen it over a dozen times already this autumn.

Here it's 16.5C downstairs, 18C upstairs and 13.7C outside.

Excepionally mild 14.3c outside.

[referring to condensation on the outside of the window]

The incident I referred to was in 1964, single glazed windows and probably not altered since the house in question was built in the 1930s