Well, I'm sorry to be stating the obvious here, but you were leaving yourself open to disappointment if you put a deposit on another house if the proposed purchaser of your own property hasn't signed contracts.
Likewise, if you haven't signed contracts on your new property, you are perfectly entitled to withdraw.
Banks are very reluctant to offer bridging in a situation where contracts are not signed on the house you're selling. I would re-think your situation if I were you.
Sorry about your bad news