Sunnyjohn
As True Blue has said next winter's flights are not on sale yet. The nornal ruling is the winter flights go on sale as the summer schedules starts (that is the end of March) and likewise the summer flights go on sale as the winter schedule starts. In other words you won't find two the same seasons on sale at the same time.
And by the way GTW was the code for Gatow in Germany. LGW is Gatwick.