In front of a passenger, I would address him or her as Captain "Smith" or whatever. Other than that, it's always been first names really. I've never come across a pilot that has been asked to be called anything but that. I think the fact that at BA, they introduce themselves when boarding the aircraft and making the effort to walk all the way back to Doors 4 to say hello shows that they don't want any "barriers" as such. It may well be different on other airlines, particularly those in the Far East.