Your reply was eagerly read and fully understood.
Your needs are quite different to ours as we have rooms that are sometimes not used for several days in the week, so they are just "Frost watched" for safety reasons, but seldom drop below 14-16°C, even in the coldest weather.
Our kitchen (which I recently enlarged,) has a full sized eating area with Sat TV and radio, which tends to get used mostly during the week evenings. Weekdays, both my Wife and youngest Daughter are at work, the eldest dos not live in....so during the day, its only me and both cats!!
As I am still putting final touches to the kitchen (and going in and out to the Garage for tools etc), so I do not heat the rest during the day, and if the kitchen gets really too cold (seldom), I switch on the pellets stove, which keeps the kitchen radiator thermostat off....and is even cheaper than burning Gas (or oil for that matter!)
With regard to larger radiators "over running" the set temperature, that appears to be a problem when using standard type thermostats only. I use ELV Germany radio thermostats which have a mini controller in them, (they are placed on the wall near to the sitting area in the room and control the rad valve remotely), which senses the "Rate/speed" at which the room is warming up (it learns over the first few switch ons) and it shuts the supply of hot water down slowly to achieve the required temperatures with no noticeable "overshoot" at all, not even 0.5°C, amazing.
Certainly measuring with an inside/outside thermometer (using the outside temp to check the rad water temperature) shows me exactly what is happening and the ELV valves keep the room temps to within 0.5°C of the required temperature all the time. (That is the fine limit of the cheap digital thermometer that I use, 0.5°C).
Such ELV units (or similar) are highly recommended for many other reasons too.....I do believe that they pay for themselves within a few years anyway....but for the comfort alone they are worth the extra cost.
But in any room/house with really good outside wall insulation and standard rad thermostats, overshoot of the temperature will happen to one degree or another (pun intended), then the temperature will/may hunt a few degrees up and down.....some people notice it some don't.....whether its a problem or not is up to the individual. I personally feel that younger people will not notice it so much as older folk.....but I could be wrong.
The only times when a standard rad thermostat does not overshoot its temperature is when the heat losses from a room are such that a "balance" is reached with regard to heat coming in and heat leaving.
This is only really noticeable as the fact that the rad top is warm/hot and the rad bottom is significantly cooler/cold.......for all the time the room is in.....few know this point and even less understand it fully what it means !!!
A room where the heat loss is very low, will maintain its temperature and the WHOLE radiator will cool down to almost room temperature, within 1 or 2 °C and stay that way for long periods..... an hour or more!!!
This is basically a simple test of both insulation and draft exclusion for a particular room!! I find it quite fascinating!!
But such work and study over the years has allowed me to reduce our gas usage to about 30% of what this house needed 22 years ago, but with a significantly larger boiler and a 1000x more comfort!!!
I have a boiler from a subsidiary of Bosch, it is small (28KW)and lives on a wall in the bathroom, you would have to be smaller than a Leprachaun to get inside that one!! Maybe Germany only exports the "Larger" boilers to the UK!!!! Implying that some people are large maybe!! Who knows!!