Saying, "Pleased to meet you" on being introduced to someone always USED to be seen as very non-U...ie lower-class. That was in the days when only, "How do you do?" was supposedly acceptable in 'polite society'.
(Please note, I am not criticising anyone or saying I agree with either idea above!)
"Sorry" when apologising or "Sorry?" when indicating you have not heard what was said are probably more common nowadays than "I beg your pardon", though the last is not yet quite old-fashioned.