Burping in youngsters is to be expected, but should be followed by either "excuse me", or "pardon me", once they are old enough.
(To be honest, although I have seen the advert, I have never heard it, as Mr P mutes the television for the advert breaks when we are watching commercial TV! This can actually be quite interesting with some of the ads, actually trying to work out what they are meant to be about!)
Numberplease you are not old fashioned! I sometimes wonder if it's only me that thinks giving a great big yawn in public (without either trying to suppress it or at least putting ones hand over ones face) is uncouth.