Affordable housing

There is no doubt that the UK needs more housing. Not only to house the young in the country but also those that come from abroad as immigrants.
Why not use 'pre-fab' housing to solve the problem? After the war, pre-fab houses were built to house the homeless population and some exist today. I remember in Liverpool, when I was younger, thousands of pre-fab houses being occupied , each with a small garden. They looked good and the time they lasted was testament to their durability.
They could still be built cheaply but still incorporate all the benefits of modern technology with respect to insulation and sound proofing. Why not? Let's do away with the many rules and regulations that hold back the construction industry and build inexpensive housing for all. Why can't the council's identify brown site areas, or green sites with poor quality agricultural land, that could support these homes. Not high rise monstrosities such as in the sixties, but homes that come with their own space and a garden and fences that neighbours can chat over.
Stop the nonsence that prohibits the provision of mortgages for houses with non-approved construction. In my country of Spain they build houses by a ring and beam method which is good in areas of high earthquake activity. Why is it unapproved in the UK when it is a relatively cheap method of manufacture?