Retrofitting heat pumps for air to water central heating, as is normally done in the UK, is really expensive and rarely makes economic sense for an individual household.
They are less common but available, I have just recently been looking at options that will do combined hydronic heat and hot water for the taps. The hardware isn't too expensive but the labor for that kind of install can be a lot (highest number I got estimated was $60k).
Retrofitting heat pumps for air to water central heating, as is normally done in the UK, is really expensive and rarely makes economic sense for an individual household.