When travelling between Edinburgh and Glasgow, the only reruns offered are day returns (£13.60 off peak / £26.20 peak). If returning on a different day, you have to buy two singles (£13.40 off peak / £15.30 peak). However, booking a journey to another station a bit further will give the option of a period return (eg Paisley Gilmore St to Edinburgh or Eskbank to Glasgow), for a cheaper price than two singles. My question is, which station just outside Glasgow or Edinburgh is the best one to book from/to to get the cheapest period return between the two cities? I usually use Eskbank, but heard a guard selling someone a ticket to another station (didn’t catch the name, but wasn’t Eskbank) for the same trick. Also, what is the logic behind National Rail / ScotRail (?) not offering period returns between the two cities?