Well, there have to be more rooms because in the Unquiet Dead the Doctor gives Rose a whole series of directions in order to get to the wardrobe. Since the internet has failed me, I did a quick rewatch and he says things like fifth door on the left. Honestly, I would be upset if there wasn't a giant Beauty & the beast sized library there.

I will spare you my Tenth Doctor wibbling, but it seems that without my will, he has grown on me. Somehow. I believe that it is his superpower.