I rather suspect, despite the advice given in that work of fiction, namely the "Protect and Survive" booklet, that should you have seen those bright flashes in the sky or anywhere else, then you would not have had a home and, should you have survived initially, you would have not lasted very long thereafter.
None of us know how many (if any) would have survived, but evidence from Hiroshima and Nagasaki suggests a reasonable percentage of the population some distance from a small-scale event would have survived. And the risk wasn't just about an all-out war, there was also the potential for USAF personnel to get a bit careless or unlucky.
It has become quite fashionable to mock "Protect and Survive", but some of the comments are based on a misunderstanding of what it was really about. Obviously you won't survive if you are very close to a nuclear explosion, but for people further away it was important to know what to expect and to use simple mitigation techniques to try to maximise the chances of survival.
We've actually seen the same thing with coronavirus. The initial advice about washing your hands was subjected to ridicule, less so now.
In terms of the 1980 booklet, the statement "Everything within a certain distance of a nuclear explosion will be totally destroyed" (page 5) wasn't fiction. Neither was the advice on page 14 (to stock food for 14 days) or page 15 that reminded people of the need to have soap and toilet rolls.
Taken as a whole it may well have had more value as propaganda than anything else, but the kernels of advice contained within it were true, and many of them remain relevant today.
