The first task
This is the night mail, crossing the border. Where is she pulling up? That's the password to the Night Mail page. The username is nightmail. Use lower case throughout.
The second task
You are in control of the Night Mail. You need the name of the first Pullman, and of the second Pullman. Use all lower case. That's the username and password to this page
The third task
This is a night cache. You'll need a good torch.