There is a very interesting document on Civil Defence from 1951 as part of Cabinet Minutes from the 27th of January that year.
Despite crippling post-war austerity, the government had decided to increase spending on Civil Defence from £137 million to £180 million over four years which is more than £5 billion in today’s money. Even in 1987, the UK was spending only £69 million (£170 million today) despite facing a far greater threat.
The most profound comment in the document however is that it admits to the basic contradiction in both Civil Defence, deterrence and in that they are part of the same:
the Defence Committee considered that, quite apart from the enormous cost that would be involved [of a large stockpile of blackout material] , any general acceleration of civil defence preparations would give the impression that the the Government regarded war as inevitable.