Good, we're desperately short of housing, hence the ridiculous high prices for houses and rentals.
Immigration, rising populations, and expansion of universities all cause more demand for homes, plus in tourist areas, huge numbers of homes have become holiday lets especially due to covid, travel restrictions, rise in air fares, plus increasing numbers of family break ups, one parent families where two homes are now required instead of one for the family, etc. University accommodation and holiday lets are particularly problematic as they're not occupied all year and are lying empty for many weeks of the year. Family homes have been lost to Uni students and holiday lets and new homes aren't being built anywhere near fast enough. Broken families often mean one of the parents "needs" 1 or 2 spare bedrooms just for weekends or holidays for when their kids come to stay, so again, increasing demand for larger housing etc. None of that is going away, so we need to build more homes, and in great quantities.
We can't just sit back and pretend we don't need to do anything. Either the government need to control holiday lets or stop the Uni expansion (or encourage students to live at home and go to their nearest Uni), or try to stop immigration. All of those are problematic, so the obvious answer is to build more homes!
Yes, hopefully more brownfield sites would be used, existing unused city centre buildings redeveloped or demolished for housing etc., but that's already happening in many Uni cities with old buildings being converted to student accommodation, but it's just not happening fast enough. But also, yes, there's lots of green land not built on that could be - trouble is, there's no "big" thinking into making new towns, the new building on green land is usually lazy/cheap "urban sprawl" just making existing towns bigger, without putting in new infrastructure. Whereas carefully planned new towns, with new infrastructure is the real answer, but that costs money and will be unpopular with the voters.
It's a bit like the flagging economy, debt, etc., really. Voters are in denial and are NIMBY's, they want homes built "somewhere else", just like they want "someone else" to pay more tax to improve public services, etc. We need to get real and accept things have to change and that such changes will affect ALL of us, voters can't just constantly expect "other people" to suffer the consequences - when they do that, we end up with politicians too frightened to tell it as it is, and so the can just keeps getting kicked down the road.