Flights with easyJet are due to open in April. Even booking the day they open doesn't make them much cheaper if you're going in half term though.
We were due to go to Salzburg in February half term this year. Last April I was up at 5am on the day they were being released (6am release time). Couldn't bring them in under £2800 return for a family of four. Changed the flights to the week before and got them for £300 return. So we pulled them out of school for a week.