Anybody looking for inconsistencies should check out Michael Portillo's Great Railway Journeys. Interior shots of Voyagers, 153s and such and then external shots of HSTs▸ . Even an interior shot of a HST and then a glance out of a window with a hopper on the top!
Point is - ONLY - rail buffs would notice that. I personally would just assume it was convenient editing.
The ER thing was just SOOOOO obvious. However in the same Epsiode, Corday was in a London hospital and the plug sockets behind were clearly American sockets as were the light switches ....... although come to think of it - only her and two other actually spoke (the accents were NOT accents) so its entirely conceivable they got English actors.
Yet the external shots of her n a roof near tower bridge were not superimposed so I guess they flew her back to England for location.
Note - I edit my original post here - I meant TOWER bridge NOT London Bridge