Hi, we are thinking of buying a house that's currently on storage heaters (village has no gas). I'd love to get an air source heat pump with underfloor heating. Issue is its 1930s - so no insulation in the solid ground floor. I've seen you can either dig it all out and start from scratch (very expensive), get an overlay system that raises the floor 20mm (less headroom/all door/skirting needs changing) or get milled channels in the existing concrete. Every forum I see has someone saying the milled type is throwing money into heating the ground but no one seems to have any direct experience of it. officially only 10% of heat is lost through the floor, however that doesn't account for heating the concrete directly! So, has anyone the channels cut in there floor in an older house? Was it a nightmare and cost a fortune to run/didn't heat up? comparisons also switching to an air source heat pump also welcome! Thanks