I think railway stations are owned by the government -- which I think means you can.
But my advice is not to ask if it is ok or not ok wherever you are. Most people don't mind. Also, I've been asked to move on a few times, but, I just tell the council people "call the police"..... they really cbf doing anything about it normally lol. So yeh, just go and leaflet, the worst is someone will ask you to move on -- you can't be fined or arrested without being told what you're doing is illegal.