Can confirm that in my 1920s house, now with heat pump, my energy use is now a fraction of what it used to be, since replacing boiler with heat pump.

Before: Jan 600kWh electricity, 3300kWh gas = 3900kWh

After: Jan 1580 kWh electricity, 20kWh gas (cooking hob)

So in total, 41% of previous amount, and for heating, 30%.

So yes, for crappy uk houses heat pumps are totally fine.

Adding in solar pv, and a time shifting battery, and the bills are maybe £2k per year lower than they would be.