you really need scale for sand batteries to work

Not at all. First, (hot) water batteries are excellent for home heat storage. Sand/dirt is even more storage per volume required, and completely complimentary in sending hot water through it (pipes) to make it hotter. No combustion heat means less air exchanges, and a 300C rock/dirt/sand pit has losses that radiate through house.

Suburbs are fine for district heating, but it's a massive long term investment.

For UK in particular, I also think proper insulation and triple/quadruple window panes are much needed to curb with the increasingly scorching summers and freezing winters. I was surprised to see soo many houses with single paned windows in London.