Not my area of expertise but about 5 years ago as part of a project funded by EDF to look at alternative energy uses in the home, we looked at air source heat pumps for three domestic properties that were built in the 80's. To make it a viable source of heat, the upgrades required to the loft insulation, cavity wall insulation, GF flooring, windows & doors, meant it wasn’t viable for the project.
As an alternative we installed solar panels & a district heating system with a gas CHP boiler.
Unfortunately the installer didn’t change the electric meters from analogue dials to digital, so through the day with no one at home they went backwards. “No one noticed” until one tenant went away for summer holidays, got a negative bill and then was being pursued for fraud.