One thing that comprehensively confuses people using UK railway train reservations: The 'A' suffix on your seat number doesn't matter. When you have a reservation for 44A that doesn't actually mean there is a seat 44A distinct from seat 44, it's because somebody thought it's important to bake in metadata about how seats are arranged in trains, the A apparently stands for "airline" style for some reason.

If you hate reservations or are too disorganised to book one for a busy train, but also dislike being disturbed by someone who does have a reservation and wants you to move, most train operators have some rule about which parts of their trains aren't reserved, you can find that out and then travel in the unreservable part of the train. Finding a seat there won't be any easier, but you won't be asked to move later.

It is interesting how trains are offering better services even as planes suck more over time. Ten years ago knowing where to find power sockets in the Standard class 444 series (next to the cab at the far end from First class) made the difference between charging devices and going without, now almost every train has power sockets and/or USB, free WiFi (not _good_ WiFi, you won't be streaming video - but it'll let you check email and read Hacker News) and air conditioning.