Okay so I adore your story and you write the Doctor really well. I personally didn't know it was possible to write him like that given he's so..... well..... Timelordish. But it fit and your interaction between the Doctor and Gwen was awesome. I love the idea for the story too.
So here's my one piece of critisism.... Barty was just a bit out of character for how J.K. wrote him but I do think for here it was necessary, you just might want to specify in the author's notes if it was intentional. Otherwise I think it's awesome! Good job and I look forward to more stories from you.
I loved it.
-kayt