Being new-ish to the industry (and very new to this site), what is the general opinion of heat pumps as the primary source of heating? I've been told that they aren't much good in the depths of winter, but I've found that the Whirlpool (£250) heat pump I installed in my bedroom works superbly! (UK climate).
I'm just about to do an install on a friend's newsagents shop, which is currently heated by power-hungry 3X3kW single phase electric fan heaters. I think he could rip them out (or at least stop using them) and rely on the heat-pumps, and save an absolute fortune in heating bills... am I correct... is this wise?

Any thoughts!