To take benefit of the best prices you will need to prove you are not a business traveller, en route to luton airport, so you will need to give either yr flight numbers or your holiday booking reference. I don't think you will need to provide this when you arrive at woking station but you may be asked to provide them on your journey from the station to the airport.
Going to luton airport on the train is great, you can sleep, read a book (even at night), play travel scrabble, or just gaze out of the window... The other caveat to buying these cheap train tickets from the station to luton airport is that there must be at least two adults travelling together. But another great advantage is that children go free. All kids under five go free, and then one child over five but under sixteen per adult travelling by train to the airport.
be sure to leave enough time to get to the airport early enough to eat, shop and so on, so check the times of trains from the station before you go. If you end up with spare time at luton airport you can always read a book or play travel scrabble again! As you have bought yr train ticket in advance, you don't need to fret about the opening hours of the station.
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