Hilda has a point. While going over the list of supplies that one should have for one's refuge, Jim reads off a pen and a notepad for writing messages. In a nuclear war where humanity is dead or dying, WHO would you write messages to/for?
Notepads and pens were probably in a best-case scenario, if the government or society is still functioning at that point.
The instructions are placebos intended to serve a political purpose (making it appear that the government is "doing something") rather than actually intended to serve any useful purpose in the face of a genuine nuclear attack. That's the entire point. So the pen and notepad are included specifically because they are hopelessly inadequate to reality - making it seem like a fun boy-scout-style exercise in preparedness rather than actually preparing for the horrifying reality of a nuclear war.
Considering that the pamphlets suggested they get into paper bags ( which they do as they're dying), the idea of writing notes was more like "best case" scenario so the Powers That Be could identify the deceased. Other than that, Hilda had a point, considering some of the other things she's pointed out. Realistically, none of the things they were told was effective or useful.
You're not going to be keeping up all your correspondences, but even a nuclear war doesn't mean literally everyone dies at exactly the same moment. There may be survivors wandering around, you may need to communicate with them somehow, so having a pen and paper with you might come in handy.
Exactly how old are the Bloggses?
Jim and Hilda are consistently described as being elderly, or as a couple of pensioners. But this is at odds with the time period established; the second World War ended "forty years ago" according to Hilda, and both Hilda and Jim are depicted as children in their respective wartime flashbacks. This puts the pair in their 50s at the latest. And even if you were to argue that "old age" is subjective, that doesn't line up with them being pensioners, as the State Pension age in the UK has never been younger than 60.
Perhaps it's a case of 20 Minutes into the Future, an alternate timeline set 5-10 years after the time the comic/film were released.
That doesn't explain how Jim and Hilda seemingly aged from children into old-age pensioners in, what is explicitly stated in-universe to be, the span of forty years.
The "forty years" is really vague. Presuming they were referring to WW2, then for their respective ages to make sense in the movie, that would be mean that they were born in the late 1920s or, rather, very early to mid 1930s, got married sometime around the 1950s or 1960s (going by their fashions), thus they would be in their sixties, which could set the film either in 1986 or a little afterwards in the 1990s. Alternatively, that line was prolly due Jim's absentmindedness, in that, to him, WW2 was about "forty-years ago" in the vein of "it was only yesterday" and, in 'nother line, he called himself and Hilda "middle-aged".
Jim on National and International Politics
Jim is shown reading newspapers and is implied to follow current events on radio & television. How can he be so naive about worldwide geopolitics and even his own government? He actually thinks that Bernard Law Montgomery is still a general in the British military!
This is meant to show how out of touch he is with the new conflicts and war powers. Remember the Jim and Hilda have nostalgic memories about the bombing from the last world war and think this is the same not knowing this bombing is on a whole new level.
