Whichever I feel like at the time.
I do remember having a lot of fun a while back in London trying to get directions to the nearest NR station (I think I had my bike with me). Asking people who's primary language for the nearest "National Rail" station, "surface" station, "big train" station, "not tube" station.
Drawing the arrows of confusion got an "I don't recognise sorry"
I should have done more variants with the "train" and "railway" station to add even more confusion!
Some people refer to all NR services in London as "Overground", even though only certain services are branded as such. Don't know why this annoys me so much
I rarely use "train station", instead using plain "station" or adding DLR/Underground/Tube etc to the beginning.
