During the scene when the Doctor is on the motorbike traveling through London I noticed the camera and crew reflected in the Doctor's helmet! Surely they could have sorted this?
Interestingly the hurried announcement of Tennant and Piper's involvement has come about because it was printed in Doctor Who Magazine - to be published on Thursday - but subscriber copies were distributed early. Surprised they were happy with that arrangement to be honest, when I subscribed in the 90s you could get your copy either a week early or up to a week late, sounds like it hasn't changed!
It's normal for subscribers to get their issues of any magazine a few days before it hits the shops. If they didn't want to announce it yet, it should've been held back until the next issue.
Cumbria as a name stems from the ancient Brythonic (Celtic) word for "Brothers" or "Countrymen" (it's the same root as Cymru / Cambrian). As such the word certainly predates the modern placename, but it is conceivable that the region gained its name well before the C13th.