I’ve used trains fairly regularly. I buy my tickets using the Trainline app. For the last journey, I bought the ticket 15 mins before departure. It was last Saturday and we were headed to the countryside for a walk, but the train was packed with day trippers to the seaside. There was hardly any seats left, which shocked me. Returning, there wasn’t many on, and my son picked a table seat. I didn’t see that the seats opposite what he had picked had signs saying ‘Do not sit’ as I came from behind them. I got asked to move which I found rather bizarre considering the circumstances of the outbound journey.
Anyway, most journeys I have been on have been fine, with no problems. If you buy your tickets with Trainline and don’t use them, it is easy to get a refund, but they take a charge depending on ticket price.