When Kate is sitting waiting for the last train, there is a close up on her legs, showing that she's wearing black fishnet tights. All through the rest of the film she seems to be wearing sheer black tights.
When the train that Kate boarded at Charing Cross comes to a halt in the tunnel, she goes to the front of the train where the car number above the door to the front cab reads 96101. After the lights have gone out and the nasty boyfriend has activated the emergency lights, Kate returns to the same front cab door and the car number has changed to 96107.
At the start of the film, Kate is wearing black tights with a small fishnet pattern. During the running around in the lower levels of Charing Cross they have become plain black and remain so for the rest of the film.
The unexpected train that Kate boards at Charing Cross and where she is followed by Guy is a 1996 Stock Jubilee Line train. When she runs into the cab and gets out of the train into the tunnel the train has switched to a 1972 Stock Train.
Kate runs to the rear cab of the train and passes through the cab door (car number 96115 displayed above it) however the cab interior and exterior is of a car of long since withdrawn 1967 type stock (car number 3329 can be seen on the outer door behind her) whilst the train she was actually on (car 96115) is modern 1996 Jubilee Line stock.
A large station like Charing Cross is rarely so quiet as it is in the movie. Usually there are no end of contractors and cleaners walking through the station after the last trains have left, in addition to the Station Supervisor.
The cannabis dealer at the beginning of the movie says "...that s***s legal now." referring to cannabis. Actually cannabis has not been legal (as of 2015) since 1925. During the early 2000s it was downgraded from a Class B drug to a Class C drug but it was never legalized completely.
Franka Potente's character falls asleep accidentally and thus is left at Charing Cross after closing time. When she awakes and later on luckily jumps on another train passing through, her rude admirer is there to greet her (and then tries to rape her). He would have had not only to stay hidden all this time while following her, but also would have had to accept being locked in with her, plus would have had to wait for her while she was frantically trying to get out only then to return downstairs trying to catch this last unannounced train.