There's loads of houses being built in the UK (often of questionable quality, built for maximum profit, packed into minimal amounts of space). It may still not be enough to match the demand, but the real problem is we don't seem to be building any infrastructure to support these homes. More people and more homes requires more roads, railways, hospitals, police stations, power stations, sewer capacity, even reservoirs…
We need to build houses at least as fast as the population grows. Because this has not happened for decades, we need to build houses even faster than that, to clear the backlog. This is not happening. Meanwhile, no-one will build infrastructure for settlements that do not yet exist, and we consistently elect a party that believes in less, rather than more, infrastructure in general. Rather than an investment, Tories…
And this is both how it ought to work and means that the UK has a lot of existing rail that could help solve this problem if the government would just commit to streamline planning processes and to increasing routes and frequency to stations where there is a potential for density increases at lower cost.