Although their website said submissions would be acknowledged and decisions given in 3-4 weeks, I heard nothing. I resubmitted, and still heard nothing. Now I have discovered that their Twitter account has not been used since July. Just my luck!
They were a very good fit with my proposal, too. They have (had) a series called Bitesize History, and my proposal was a book about the Magna Carta for the layman. I have now sent the pitch to another publisher, but I haven't had an acknowledgement from them either. Oh well.
It's not all bad news. The idea for the book has taken hold, and I've decided to write it anyway. It will be released as an ebook.