ok first off loose v lose as it is all through this thread. phew, needed that, sorry.
Secondly, did you put any "subject to" on the deposit? I paid one subject to scertain things being made possible by the dealer, they couldn't do it so i got the cash back no problem.
You could always say you'll be off to trading standards as you felt pressured to sign at the time which to be honest you probably did. every salesman will give it the "i've had a word with the manager...." and "if you do the deal today...." etc etc.
5t.