Actually, the engineer controls the train's movement in & out of the station. The engineer is in control of the train movements with one exception- when a train is put together. A hostler...
Well, On the Aylesbury to Maryleone line, only Chiltern Railways are used but the mainline on the west cost uses Virgin. Banbury is the only station where these two collide
All depends which station in Kensington - go from Harlow Town to Liverpool Street on the train, then take the Circle Line (in either direction although eastbound's probably a bit quicker) to South...