It was Christmas Eve 2013 when LGW went into meltdown wasn't it? Flooding killed a key generator or something. I had an evening flight to EDI that was cancelled in the morning. I was extremely proactive, booking myself on an earlier flight from LCY immediately, and then dealt with the cancellation and money part later. Everything worked out fine. I've travelled every Christmas Eve since and never encountered a problem. Went from LHR last year, in order to more enjoy the festive spirit.