Unless you're going on your own, buy your tickets in pairs. Get a duo ticket, it's a buy one get the second half price deal. They're supposed to offer you these when you buy two tickets together, but they often don't. It works on most train journeys apart from Barnsley to Sheffield because I think you've got to cross a county border for them to become active. They're only for returns, but for those doing the walk and coming back by train it's cheaper for two of you to get a duo return than it is for you both to get a single from Chesterfield. Single from Chesterfield - £7.40 Duo return - £11.40, so £5.70 each http://www.northernrail.org/tickets
I followed your advice Jay and pre-purchased return duo tickets at £11.40. How bloody typical was it than no bugger came to check our tickets all the way back to Barnsley. Could have save £11.40 :frown: