No one is going to wipe our London overnight with junk food. And I don’t eat that ****, so have little to fear from it personally. Nuclear war, on the other hand, I believe we all have good reason to fear.
Good to hear you are staying healthy.
If it bothers you, there are careers/fields of study to pursue with DOD. Otherwise, research local shelters, make friends with someone in the country who would not mind if you joined them, what else is there to do? Life is filled with all kinds of dangers, do what you can - worry just makes life miserable.
I had family friends who were preppers- stockpiled food, guns etc, off-grid - spent their entire life paranoid. Their food spoiled, they died of old age - could have spent life enjoying vacations instead of living in bunker.
Serenity prayer, do what you can, then let it go.