obtain a "customer comments form" for the relevant train company for the disrupted journey (if Edinburgh presumably Scotrail or EastCoast), complete the form indicating the train on which the problem occurred and attach the train ticket for the journey. The extent of delay occasioned will determine the amount of recompense, but it will be provided in the form of travel vouchers, not cash or cheque.
during a period of disruption caused by flooding last year, a delay of 3.5 hours got me £45 worth of vouchers from virgin trains.