That's what I am going for Martin. i discussed underfloor and the builder said yes, you'd have to dig up all the tiles and bits of the concrete base. Big job. Also it depends how you power it. The place I stayed, they had the whole solar caboodle with batteries so the energy was saved. Took up masses of room and must have cost a fortune to install. If you don’t have all that, presumably it is very costly to run on electricity.
So I will see how the air con solution works. Only going for it in the bedrooms at the moment as cold, damp bedrooms are the worst and will see how we fare with a gas heater and wood fire in the living room.
Another option I have encountered is people running a kind of limited central heating system, with gas, using the big gas bottles. Presumably the gas heats some kind of boiler, According to the owner who had that system, you were forever changing gas bottles as it ran out so fast.
My bathroom has those electric bar heaters which blast out the heat, look dangerous and probably cost a fortune to run. I am wondering whether electric towel radiators would be enough, keep the towels dry in winter and maybe a teeny bit of heat, instead of the electric bar heater. Also for safety, presumably, the bar heaters are over the door, I can’t see how that warms the room much.