We don't say mate much anymore, I only hear it occasionally. I don't like it because mostly it's used passive aggressively when they're trying to intimidate you. Like false friendliness. My manager called me mate yesterday which I didn't like. But generally, no, I don't find these terms offensive. If someone calls me dude, I don't care. I call people dude, too, just from habit. The only ones I dislike are when guys call me babe or anything like that, or refer to me as a chick. But that is for entirely separate reasons. Here in London, boss is popular for some reason. Usually like "Ey, boss, 'ow much is dis?" because all our accents are screwed up from the posh/cockney/afro-caribbean influences. I know a lot of guys who hate being called boss, but I don't really know why.Oh btw Merc and JC don't speak for England they speak for a savage torn up area that stinks of booze and inbreeds, I however speak for England, I ensure you we do say mate around here a lot.
Also, we don't really say bro, we do say 'bruv', whether in reference to your actual brother as it's used in the home, or just friends, or sometimes even to enemies. I remember seeing some guys arguing once and they were like "BRUV, BRUV, BRUV" haha.