To take benefit of the best prices you will need to prove you are a leisure traveller, en route to glasgow-international airport, so you will need to provide either your flight details or your holiday booking reference. I don't think you will need to provide this when you arrive at the station but you may be asked to give them on yr travels from the station to the airport.
Going to the airport by train is great, you can take a nap, read (even at night), play travel scrabble, or just gaze out of the window... The other restriction to buying these inexpensive train tickets from west-hampstead station to the airport is that there must be at least two adults travelling together. But another great benefit is that children go free. All kids under five go free, and then one kidover 5 but under sixteen per grown up travelling by train to glasgow-international airport.
be sure to leave enough time to get to the airport early enough to eat, shop etc, so check the times of trains from the station before you go. If you have time to kill at the airport you can always read a book or play a game again! As you have bought your ticket in advance, you don't need to fret about the opening hours of west-hampstead station.
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