Air Source Heat Pumps - has anyone in London installed one?

Maintenance

I've been looking into Green Homes grants as the boiler in my rental is 16 years old and it's not clear what will happen with the Govt looking to phase out gas boilers. It seems pointless to replace it in a few years only to have it potentially become illegal a short(ish) time later. It seems to be a no brainer to apply for a grant to replace with an air source heat pump (primary measure) and then replace single glazed windows (secondary measure) now while the funding is on offer. However it's difficult to find information on good installers and my plumber told me that these heat pumps are generally used in rural areas. I wonder about the noise from the outside unit in close proximity to neighbours and possibly needing bigger radiators as they don't give out as much heat as a gas boiler. I also don't want to install under floor heating (as recommended with ASHPs) & wonder if it's really necessary in a small house? Has anyone had one installed? If you have any info on your experience of them or any advice on what to look out for that would be great thanks. Also does anyone know of a good installer in South London? Or any idea how to get a recommendation?