Building a nice house is simply expensive. Being able to afford this is a wealth that has to be created first. A strong economy with skilled, highly paid workers is probably an essential requirement.
What can the government do about it?
- Invest in education
- Keep taxes low by not squandering the taxpayer money.
- Maybe lower safety and environment standards to lower building costs (but this may be a very dangerous road to go down, see Grenfell tower fire in 2017).
Land is scarce in highly populated areas like South England. This really drives up the cost of the land which must be procured before a house can be built. In some areas, there is simply not much more space available. And there should be some land left for recreation or just for natural reserves.
What can the government do about it?
- Not much, maybe encouraging migration to the North by diverting resources and administration centers from South to North England (and Scotland)
The house price is also determined by supply and demand. If many people want a house, but there aren't enough, prices will go up.
What can the government do about it?
- Aim at increasing supply by financially supporting the building of new houses (maybe by tax advantages and cheap loans)
- Tax unused/undeveloped property really, really, really high
- Provide new areas for housing
- Build houses yourself and sell them
If lots of more houses are built, the prices of existing houses will go down too.
The alternative - what is "affordable housing" really?
Housing maybe doesn't mean having your own mansion. Aiming smaller (smaller living space, more highly integrated and densely packed) may reduce costs and land requirements, so that a smaller kind of wealth is more easily affordable. Small housing is probably more affordable housing.