We had an event at a local old village hall on Saturday. Maximum capacity 100 people. The hall is heated only by four wall mounted heat pumps sited at just over head height. The hall was cool. The heat pumps were struggling. The outside temperature was 6 degrees C. After turning on via a remote control unit, flaps slowly open on the internal units and warmish air comes out, which seems to flow upwards to the ceiling. With wall mounted radiators at least they are located lower down and can radiate some heat at leg height, or people can stand next to them if really chilled. I am not impressed with the heat pumps.
Z.