These are among a row of 16 prefabs built in 1945 and all listed Grade II. This is the link to the list entry of the northernmost, No 397:
Link It comments: "The group of prefabs in Wake Green Road is an unusual surviving example of a rare variant of the Portal bungalow, that is still more remarkable for its exceptional state of preservation with few alterations." Most are still occupied.
The occasion was a heritage open weekend. The prefabs attracted many visitors. Two or three were open to explore, one by the Prefab Museum
Link that included an absorbing display by the Twentieth Century Society
Link Inside, though small, they felt homely and well-planned. I'd have been happy to live in one!