It was definitely not an up & coming area in the early 70s, but inflation was part of it too - my parents bought their house with a half acre of garden in the green belt for £5000 at about the same time.

Wow, even adjusted for inflation that's like £40k. You'd be struggling to find a warehouse anywhere near central for £4M these days.

A prime example of how metrics of inflation are absolutely and utterly absurd, and generalises to domestic housing as well as commercial property.