I did look, the idea was it can also cool in summer, but it seems all existing plumbing will need replacing, the bore is not big enough, and it will need all new radiators as to heat and cool they need to be fan assisted, and also needs condensate piping to take the condensate away, and outside units need planing permission, to ensure any noise does not upset the neighbours, and the £7500 grant would hardly touch the extra expense.
So a small self-contained unit just for the living room could be on the cards, but whole house was a non-starter.
I and I am sure many others heat rooms as and when required, I don't heat whole house if it's not needed. And the heat pump does not run efficient at a reduced output, well neither does the oil burner I have now, but the difference in efficiency heating two radiators or fourteen radiators is not as marked with an oil or gas boiler to with a heat pump.
Not sure on oil price now, was costing me £600 a year approx, so heat pump may be twice as efficient, although I think unlikely, so 75 now, so maximum is 25 years, but more realistic 15 years, so £300 x 15 = £4,500, it does not get anywhere near working out better.
Plus for it to work in a power cut, as my system does now, we have to add the price of huge batteries, so it becomes a non-starter.