Apparently "14% of UK greenhouse gases come from our homes, a similar level to emissions from cars. In major cities gas boilers are also a main source of nitrogen dioxide emissions."[1]
The standard is still storage headers and other wall mounted electrical heaters. I remember those from childhood, and how happy we were to switch to gas-fired central heating.
There are electric boilers which can power a hot-water based heating system; they are substantially more expensive to operate than current gas boilers (due to the UK price differential between gas and electricity).
My most favoured approach is an air source heat pump, and larger radiators/underfloor heating to make use of the lower temperature heat source. More expensive to install and run than a gas fired central heating system.
Perhaps in the house after next, this will be standard - or I might even be able to buy a Passivhaus.
Underfloor electrical heating is apparently a lot more efficient than radiators, e.g. because you only need to run them at a much lower temperature. If you combine with things like ground source heat pumps and solar panels, the electric heating proposition looks a lot more appealing.
That said, the conclusion I came to is that for an old place that doesn't otherwise need major work, it just isn't worth the expense of making the switch. It might be that if I were to move somewhere that needed a complete refurbishment anyway, then I would. Even then, with most homes, at least in cities like London, being flats rather than houses, then things like solar panels and heat pumps become much more difficult if not impossible to arrange.
[0] https://www.designingbuildings.co.uk/wiki/English_housing_st...
[1] https://en.wikipedia.org/wiki/Prefabs_in_the_United_Kingdom
[2] https://www.theguardian.com/society/2009/mar/17/historic-pre...