I've had a few heating engineers in recently as the 25 year old gas boiler is very much on its last legs, so looking to get a new one installed before those get banned.
I was interested in whether it was worth getting one that can run on hydrogen mix as well as gas just to future proof a bit.
Discussed heat pumps with all of them and there was a lot of laughter and eye rolling. You need a considerable amount of space for all the tanks, and pipes need to be replaced with larger bore and larger radiators.
We have no ceilings in a lot of rooms - just the floorboards of the rooms above. There is zero insulation, and to keep the house dry and safe from damp it's really important to have good ventilation. Heat pumps need nigh on hermetically sealed boxes to work efficiently. There is no way that one could ever be installed into our property - it wouldn't work, there is nowhere externally to sit the pump and the Conservation Officer would have a fit.
Good news that you were allowed to put in the vents! Mine seems to do that all by itself - I can see daylight through the walls in huge numbers of places at certain times of year. Upside is that we have no damp issues except in the cellar.