[RobinL]

Yes - good point.

That touches on another myth I've heard frequently - that heat pumps are only suitable on well insulated homes. I think this may be true in relation to some air-to-water systems (?), but it ignores the possibility of just installing a cheap air-to-air system on top of existing heating (either gas or air-to-water).

Air to air systems are really well suited to homes with a combined kitchen/living room which is the main room in use most of the day. We only heat the kitchen/living room during the day (our main living space), and the heat pump is more than adequate for this. It typically uses around 10kwh a day for quite a big, not very well insulated room.