easyjet never go down if they do go lower than what you payed you can a voucher for the difference from them
You're quite right Chris, just found this in Easyjet terms and conditions.
Easyjet Price Promise
Article 26 Price Promise
26.1 If You have, or the Booker on Your behalf has, made a Booking directly through the Website and You, or the Booker, subsequently find that lower fares (when taken together with all applicable fees and charges) for the same easyJet Flight have become available, You will be refunded the difference as a credit voucher against future Flights on easyJet. The only exception to this “price promise” is if the lower fares have been offered as part of a promotional offer that is launched after You have purchased the Flight. For the avoidance of doubt, this Article 26 will not apply to any Booking made on Your behalf by any licensed third party booking systems (e.g.: travel agents, screen scrapers) or through easyJet’s Call Centre.
There are further conditions, the main one as far as I can see is that the vouchers must be used within 6 months. Another condition is that you telephone the Customer Service Team, they won't accept emails, fax or letters.
I've not known any flights that we've taken with Easyjet to drop in price to date, but I'll definitely keep an eye on them, you never know.