After posting this I watched Threads again.
First time in years.
It was still extremely creepy - I'd forgotten how it drew you into individual characters' lives. But almost as much as that it was a snapshot of my childhood. Eighties cars and attitudes, casual sexism and snobbery. I have a tendency to think things haven't changed much, because the change happened slowly all around me. Simple things like old cars and telephones and pubs really bring it home.
And no, I didn't watch Life on Mars