As I have said on the other heat pump thread. Why can we not just replace gas boilers with electric boilers? They cost about £1,000, are quick and easy to install, with no need to fiddle around with the rest of the system. More expensive to run, but heat pumps are not cheap to run and many homes will need to supplement them with other electric heaters or wood-burning stoves.
Heat pumps are a good idea for new properties, but, as Scones says they are very noisy. Just imagine a run of little late 19th century terrace houses, backing onto a similar terrace, both with small backyards containing heatpumps, the racket will be horrendous. And what about flats, will they have one huge noisy heatpump on the roof or will each flat have individual heatpumps installed in a window, all buzzing away.
Heatpumps, except in new build, strike me as a very complicated solution to a relatively simple problem.