I smiled and shook my head when the girl told her friend to turn down the music blaring out of his phone in case it annoyed anyone. Instant brownie points - they thought I was nice because I wasn't tutting. I laughed at them when one boy spilled his vodka and lemonade all over himself, and I offered to take pictures of all 3 of them when they were trying, somewhat unsuccesfully, to do it themselves.
Then they pounced and insisted on photos with me too. They were a fun bunch - having decided not to insert the phone into a place where the sun doesn't shine and rather practise some tolerance, it resulted in a lovely interaction with some kids who were just out having some fun, not harming anyone but themselves. One of my better decisions. They were last seen waving and shouting 'I love you nice lady' at Hersham station.......
p.s. and the young lady kindly emailed me a picture! A great night was had by all, apparently, and no nasty heads the next day.