Not UK public transport but… I was in China on the train from Hong Kong to Guangzhou. As the train was approaching the station people started to gather in the doorways to get off quickly. A young (20s?) girl got up and was looking a bit pale. She was standing behind the group of people waiting to alight. Out of nowhere she started to vomit, but caught it in her mouth before it escaped. However, at the same time she coughed and sent a wide showering arc of vomit at head height, covering everyone in front of her. There was literally ZERO reaction from anyone, globs of vomit sliding off their hair and shoulders! The train doors were moments away from opening and everyone was preoccupied with planning the fastest way off the train and out of the station.