When I was doing some extensive renovations of a house about 7 years ago now (in the UK), we called a company whose main business was to install heat pumps (along with underfloor heating, etc). The person asked me a bunch of questions, and based on the age of the house and the insulation and such, she said, "I appreciate what you're trying to do, but I'm really worried that a heat pump won't be able to heat your house sufficiently on cold days; I'd really recommend that you take the money you'd spend on a heat pump and spend it on better insulation for the house instead."
Given that's their main business, and that she was knowingly turning me away as a customer, I tend to give some credence to her assessment. At least it can't be due to a lack of understanding or bias.
Now that our house is better insulated, I might try again next time our boiler is up for replacement, particularly if I can arrange to get the heat pump to cool the floors in the summertime as well as heat them in the wintertime.