Oh, oh! I would love to see a scene where Donna comes back to the reception with the Doctor, convinced that she needs to keep this alien secret, and Sylvia goes, "Oh, it's you!" and completely surprises Donna that she knows him.

Oh, yes, I've heard of those. Lost in Austen is one of those, as far as I know, though I haven't read or seen it yet - I've meant to. Interesting idea!