Every British person does a subconscious class calculation when they meet someone, whether they admit to it or not. You want to know if someone is "like you" so you know how to speak to them and how to relate to them. But I mess up the calculations. I've got too many middle-class indicators now from being highly educated. (That's classism for you!) So swearing is, for me, often a way to reassure someone working-class that we're on the same level and can relate to each other as such.
It's annoying, though. I don't get angry at people much, but a close colleague once tried to joke that the Pulp song Common People was about me, having gotten the impression that my working-class indicators were the pretension, and not the middle-class ones. The idea that I might read as one of those fucking idiots who pretends to be working-class because they think it's "cool" drives me round the bend.