Well, most of the time the "deposit" collected or "booking" fee collection is done only after both sides sign on some piece of paper. Commonly the tactic employed is not to call this "booking" or "deposit" but "admin" fee. And I'm pretty sure there is a clause that says that the money can only be "partially" or even "non" refundable. If you did sign on this piece of paper that says that, then legally you will prolly not win.