Photo I can remember when, back in the 50's, Dr Who Tardis-type police boxes were common. These, and other strategic points in towns and cities, were fitted with air-raid sirens to warn against Soviet attack. The government, so as not to cause alarm, made the lame excuse that they were being installed to provide an audible call to policemen on the beat! Eh? No-one in the country believed them.
Apart from military command bases, the only shelters constructed at the time were for royalty, the government, and local government officials. In the event of a nuclear strike, the rest of the population would have to crouch under their kitchen tables! See how they really care about us all?
The sirens were eventually removed, though some were still in place in the 1990s.
As to shelters, some attempts have been made to keep examples as listed buildings, with varying success. I should think that today only some military command posts would remain in a functional state.