Went past one in Surrey about a week ago, 10 police officers (mostly PCSOs) standing around, one of them with a speed gun. Like the idiot I am, I'd muted my radar detector so didn't spot it until it was too late. Was pretty much resigned to getting points, but I stopped on the way back to have a chat with them and turns out they were pulling people over then and there, so I must have been under the limit. As I was talking to them a guy in a 320d got pulled over and issued a ticket, he didn't look too pleased.