I suspect this is a version of an issue that's come up in the past about BA and humor. Without this becoming "that kind" of thread, British posters should remember that the British sense of humor is frequently inscrutable to the rest of the world. If the agent was indeed joking around, it wouldn't have been obvious to me that s/he was if I'd been on the receiving end of what OP describes.

I guess it's a hazard of being a global business originating in a country with a unique culture when it comes to humor.