What is this movie?

I saw a movie years ago in a film class that was “the apocalypse in film”. I think it was a British movie and seemed like it was from the 80s. Maybe 70s?

The premise is that a guy wakes up and is seemingly the last person left on earth. (It’s not “the last man on earth”). He wanders around high society places in London that he wouldn’t have been able to get into. Eventually he discovers there are at least two other people alive and eventually the movie focuses on the 3 of them.

Anybody know what I’m talking about?

Edit: it doesn’t have zombies