Sorry to hear about this mate, but from what I read, they do not have permission to destroy your watches unless they don't hear back from you in those 10 days. There is a thread over on RWI I think, where a member Frog something is giving advice, which seems successful too, on how to get your watches released.
Failing that, the best thing to do if they are crushed, or taken by some spotty face young scum to show off to his friends, is email Josh a copy of the letter, and he will resend to a different address.