There are two reasons why the UK does not have affordable housing:

1) land hoarded by the feudal aristocracy (parasites descended from thugs), who do not pay property taxes because there are effectively none (wouldn't want Chuck von Battenberg-Saxe-Coburg und Gotha to pay taxes, now, would we?). Most people in the UK do not own the land under their lodging due to the feudal practice of leasehold, and have to pay rent on it and are constrained from doing even essential maintenance like fire safety without the permission of the freeholder.

2) NIMBYs, generally older and Tory, who vote to block construction and are pandered to by pretty much every major party

Granted, England has twice the population density of Japan, but Tokyo somehow manages to have affordable housing.

Nor will that be a silver bullet although it will help. Do your research, people with wealth on average have less kids: why have 3 kids if you can be well traveled before youre 35? Theres too much shit to do.