No one mentioning Chris Sawyer's Locomotion? I picked it up on Steam for less than £10.
It looks a little dated (same graphics style/engine as Rollercoaster Tycoon 1), but you can easily download free mods that add an enormous amount of British trains. Just Google locomotion mods and it's one of the first links.
It looks a little dated (same graphics style/engine as Rollercoaster Tycoon 1), but you can easily download free mods that add an enormous amount of British trains. Just Google locomotion mods and it's one of the first links.