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.
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.
War does not determine who is right, only who is left - Bertrand Russell
Chichester 12m asl