That is the typical sanitised version of what would happen during a nuclear strike, and the post period of such an attack, as promoted by the UK Government in the 1970's to ease public fears. It was, and still is, crap!!
IF you had time to seek out a nuclear shelter (not two doors put into an A frame type shelter) that
actually does not exist for 95% of the population, and survive for X number of days in that shelter - what kind of life would that be?!! - you would inevitable have to emerge eventually into a land decimated by the attack. You would be in a country where no life support services exist, and you would quickly succumb to a slow, very painful, death by radiation.
We in the South East, within 60 miles of THE key target for multiple enemy nuclear missile attack, and just 100 miles from the Royal Navy base at Portsmouth, another target, and the Dungeness B Nuclear Power Plant, another key target, within 20 miles of us, our chances of surviving even the initial blast, let alone living in a post-apocalyptic land devoid of anything to live on, would be virtually zero.
That is the reality. It was during the Cold War, and it is certainly now with the latest weapons out there, such as the Russian Tsar bomb that surely they would use to make victory certain. Even 'smaller' nuclear devices, in many multiples, would do their job of destroying the main populated areas of the UK.
Any other versions of that are pure propaganda to keep us, the general public, from panicking and to keep us chugging along in ignorance of what WOULD happen. The only way to stop all that is to ensure our military are given all the resource they need to fend off any threat, or actual nuclear exchange, even if that means reducing what is spent on our medical and social services. History has proved a weak nation is perceived as an easy target for war.