Episode twelve's title has been revealed as The Pandorica Opens. This links in with the series arc as it has been mentioned before. Episode thirteen's title is still waiting to be confirmed.
Also, The Daily Mirror have claimed that Gavin and Stacey star Joanna Page could be starring in an upcoming episode of Doctor Who as a 'major character.' They say she will play "a long-lost relative of the Doctor." However this hasn't been confirmed yet.