Register with them for alerts.
We have and do receive an email letting us know the flights have been released - as samson says it will be in two phases, early summer usually september then mid June - September usually 5-6 weeks later.
I know other members have registered and not recieved their alerts until a few days after the release, but ours have always been on the day. I also think the UK Airport schedules are on a staggered release - flights from Manchester were up before the Luton/Gatwick ones, I seem to recall
Another sure bet is logging on here...someone will always post a heads-up when they are released