Last year Liverpool was early, about November 28th followed by other airports every week or so. ( If they released all flights at once the website would probably crash)
Only way to get the first few really cheap seats is to make sure you are subscribed to emails at easyjet and check your email often and have credit card ready
Wait 10 minutes and the prices might go up a bit as people book... Only the quick ones get the £9.99 seats usually.
Try Flymonarch as it seems that they are as cheap if not cheaper than easyjet and you can get them now.
The plus is its not just the first few that are cheap they stay cheap for a while. I have booked for next summer 6.30am dep for 4 people 590 which for the height of the season i feel is good and a return time of 11am