Air Source Heat Pumps any good?

[big-all]

best place to start for free honest accurate advice

https://www.moneysavingexpert.com/family/housing-and-energy-grants/

 

[robinbanks]

just want to point out that you can insulate a house as much as you like, but if it remains draughty then the insulation value is diminished possibly to the extent of being pointless. For an ASHP to work well you need to ensure your house is not only well insulated but well draughtproofed too. It is actually possible to insulate a house well enough that it doesn't need a heating system, though that is typically a "designed in" solution for new housing, but googling enerPHit should give you a starting point for research into bringing old housing up to passivhaus efficiency levels

If you go for an ASHP you may also need to change your rads or fit underfloor heating; ASHP are not a drop-in replacement for high temperature ("things that burn stuff") heating systems.. Get the fabric of the structure right first, then apply a heating system to it; the better the fabric, the less of a heating system it needs.
Like everyone else has said, getting this right involves meticulous attention to detail and understanding of thermal bridging, not letting some knuckle daggers run round with cans of expanding foam after the salesman has toddled off with his commission