I note you put the word "social" in there; very little social housing is being built, it's mostly private. Agrivoltaics are also possible, but of course everyone would rather do the politics of emotions ("hate farmers") than discuss the issues. Such as how we grow enough electricity, too.
This covers moving the UK to self-sustain by reducing animal products and repurposing animal feed cropland to direct consumption cropland; it also covers reforestation.
So while it isn't possible today, its possible to become possible without relying on any technological advancements.
Of course you can, I know people being almost self sustainable right now on very little land. It is hard, frugal but highly rewarding and we have evolved to do it since very recently.
Energy and heating is a bit more complicated. We obviously cannot burn wood or coal like we use to because this is actually very damaging to the planet. So this is where technology has to play a bigger role.
Hence why traditionally farmers either had large families, hired outside workers, or most often did both.
(Source: I grew up in rancher/farmer territory and earned some of my earliest "spending money" working for local farmers or ranchers during harvest season.)
Please run the numbers for UK farmland divided by UK population.