Pub last night at Liverpool Street Station. It was absolutely heaving. I was with two male friends. I saw a table with four chairs being used by just two people, and a spare chair nearby. I asked two people if they would mind if we crowded their space and we would try and not be too loud, and they kindly accepted. Their body language implied they were friendly enough (and they were not young people in their 20s who do sometimes appear more difficult to talk to when out). So I introduced myself and my friends to them, and we found out what we had in common and it was a lovely evening for all five ofus. I think you have to be sensitive to who you are saying hello to, but also pick your 'subject',ie person and conversation subject, and you can learn so much and be happy you made the effort.