Tim Brooks - "Steam again in Goathland", about the North Yorkshire Moors Railway.

Flanders and Swann - "The slow train" (which is on the forthcoming Patterson, Jordan and Dipper Flat Earth CD).
Roger Watson's "You can't take that on the train" (with help from Rules & Regulations of the Great Central Railway 1903) recorded by the New Victory Band on "One more dance and then". (There's a mention of the railway station in "Pretty little girl from nowhere" as well.)

And moving southwards to Australia, John Warner's "Railway Widow's Blues" (sung by Margaret Walters on "Who was here" but also included in Hen Party's new Heart Gallery show). Also, arguably, JW's Nyora Railway Journal aka Dear Diary, which isn't about railways but about the women left behind in railway camps.

But we look to the USA for great railroad songs (John Henry, Casey Jones, the railroad runs through the middle of the house. Not to mention the Chattanooga choo choo, or the trusty lariat.

Kitty