They are only being given the winter months, and even then not the month they ask. . . ."as you are asking for Nov we will give you Jan". . . Oh dear.
Despite what some people may feel about contractors you have to remember that a fair number of them didn't even choose this route but were given no choice at the end of their line-training, so shouldn't really gloat chaps.
I suppose you could say they should have seen this coming, but it is still a bummer.
The braver ones will just say " sorry guys I am not avail in Aug". . . . . the consequences of a move like that will of course depend on the market situation on the day.