According to this article, Jessica Hynes has a role in Deathly Hallows.  Upon further investigation I found out that she was the voice of Ministry Official Mafalda Hopkirk, so we can only assume she is actually playing her in Deathly Hallows.  There is a photo of Mafalda in the gallery that you can see here, and it certainly looks like her.

More on this if it becomes available!

UPDATE: Never mind! Sophie Thompson is playing Mafalda in Deathly Hallows, thanks to GigglyLipstick for reminding me of my own news post.  Now I really wonder who Jessica is playing, or if she was supposed to play her and now is not.