Definately try heat geek service – https://www.heatgeek.com/get-a-heat-pump

They have mini store cylinder that makes the unit behave like a combi boiler – very attractive option: https://newarkcylinders.co.uk/heatgeekministore/

Other Considerations

Can’t Have a Heat Pump? Could This Electric Radiator be the Solution? – Trust Electrical Radiator – https://www.trustelectricheating.co.uk/news/how_much_does_a_neos_electric_radiator_cost/
Could This Battery Boiler Replace Gas AND Heat Pumps? – Luthmore Electric boiler

Octopus Energy Offered a heat pump for #3750 when grant was at #5000. Worth revisiting

Also look at company below:

https://www.airahome.com/en-gb/heat-pumps