What a coincidence! I‘ve just spent today fiddling with Home Assistant to run a home security system. HA is extremely powerful, but trying to harness that power is very frustrating. All the guidance I can find is either very basic or incomprehensible to me with little in between. ( and I have a IT background!)

BTW heat pumps have no problem with low temperatures from an engineering perspective. They‘re the system of choice in Scandanavia where temps sometimes go as low as minus 25C. The problem is UK house design, especially insulation and air tightness (and possibly the type of heat pumps offered in UK?)