When the second bomb is being planted, station announcements are for trains to Beckenham Junction and Portsmouth which are south of London. When the station is being evacuated, Juliet Shaw says to hold the incoming trains at Reading and Ealing Broadway which are west of London.
The second bomb is scheduled to go off at 7.30pm. When the timer is down to 02:50 (supposedly 4.40pm) the girls at the cafe say it has been busy "this morning".
When Ruth Evershed is talking to the Professor Stephen Curtis he quotes something like "MacDonalds, Andrew Lloyd Webber, and Mobile Phones" referring to the bad "advances" made in the world. She replies something like "I think mobiles are very useful, and I liked Les Mis". "Les Mis" or Les Miserables (the musical) was not written by Andrew Lloyd Weber, it was written by Claude-Michel Schoenberg and Alain Boublil. However, Ruth is playing dumb on purpose to get information out of the arrogant professor and likely made the mistake on purpose.