When I asked the question of friends with new builds with air source heat pumps they said don't bother as the system is expensive to run and runs at a far lower temperature (35-45C) than an ICE boiler (75C). Further facts and comparison.
Like Jon I don't want an ugly noisy box in our garden either.
This advice also came when I asked my Central Heating Engineer, so we shall go for a replacement for our Grant Oil boiler at as close to the cut off point as possible. He said they have completed a lot of heat pump retrofits but will decline others as the customers are unhappy with the comparison with ICE.
I don't feel the cold but my good lady does so I'll stick with it no matter what they decide to charge for oil, her happy at 21C is us all happy.
2009 4/4 Henrietta 1999 Indigo Blue +8 2009 4/4 Sport Green prev 1993 Connaught Green +8 prev