I think our Lord should get rid of that dirty old boiler, replace it with an Air Source Heat Pump and save the planet! 
Not while I still have breath in my body..... 
They don't seem to work very well from what I hear.
I think you may be right Opti.
One of my friends very recently moved into a brand new house which has been fitted with one of these new fangled heat pumps. Over the last week it has become very cold down here, but she tells me the heating will only get to a certain level and no more, with her bedrooms remaining quite cold! Another friend of mine is a master builder, and is very well qualified in the plumbing, and electrical, fields. He says that the heat pumps have a limit on how much heat they actually push out, which is no where near as high as it is with an gas central heating system. 
What the hell is going on I think?!! Why are heat pumps being so enthusiastically promoted if they have limits for houses in our climate?! 
The biggest issue with heat pumps is they are complicated to setup and get working well......sadly the fitters are not up to the task all to often.
You also need good insulation, suitable sized heat emitters (radiators, under floor heating etc, to run at a lower flow temperature), and to run them 24/7 (with the hot water heating at low cost hours.
Do this and they are excellent......but you have to get over the first problem first
