I only just found out about this so thought I'd pass it on - if you've booked flights through EasyJet it's worth checking if they're now selling the same flight cheaper, if they are they will issue you a credit note for the difference which is valid for 6 months (but you can book for further ahead than 6 months)
I just got a credit note for £140 for some flights I have booked in June - result! :)