To take benefit of the best prices you will need to prove you are a leisure traveller, en route to the airport, so you will need to give either your flight numbers or your holiday booking reference. I don't think you will need to give this when you arrive at the station but you may be asked to provide them on your travels from redbridge station to the airport.
Going to the airport by train is great, you can take a nap, read (even at night), play a game, or just gaze out of the window... The other restriction to buying these cheap train tickets from redbridge station to stansted airport is that there must be at least two grown ups travelling together. But another great advantage is that children go free. All children under 5 go free, and then one child over 5 but under sixteen per adult travelling on the train to stansted airport.
be sure to leave plenty of 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 end up with spare time at stansted airport you can always read a book or play travel scrabble again! As you have bought yr ticket in advance, you don't need to fret about the opening hours of redbridge station.
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