Nobody I know uses that app. They charge way higher admin and booking fees than the alternatives.

Trainline adds a fee to every ticket sold, apps like TrainPal do the same things as Trainline (book tickets, check delays, see platform, walking times, etc), but only charge a fee if they get you the ticket cheaper than buying it from the station. So, including the fee, the price you pay is still less. And it find way better split-ticket deals than Trainline does.