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I fly easyjet all the time and it's ok. No frills sort of like southwest. You need to travel from Luton Airport which is about a 45 min train ride from Kings Cross. A bus takes you from the station to the airport. I buy at easyjet.com with a CC and have had no problems.
Arrive early as it is by boarding number. There are some nice areas to wait outside of security.
I like them to AMS it really cheap