Lack of adequate housing isn't the only thing holding Britain back, but it's one thing, and it's a thing that the government could improve with a stroke of the pen. Currently, the country has a tax on moving house - the "stamp tax" - of around 10% of the value of the home in question. It creates a huge friction against finding the correct living situation, making people hang on to a home for as long as possible. The result is people in homes that are too small, or too large, or too far from their place of work because it's just too expensive to move. If the government removed this tax on moving (maybe shift it towards a tax on occupying), people could swap situations much more fluidly, effectively increasing housing supply without laying a single brick.