After more than 40 years in film and TV, the star of Our Friends in the North is about to share the screen with Harry Styles. She talks about 90s sexism, her start in drama and playing the villain I've actually seen Gina McKee in real life once before, about 15 years ago, on the tube. There were only three of us in the carriage. I whispered urgently yet extremely quietly to my then-husband: "That's Gina McKee," and h…