Loved it.
First off, the premise is great. It's a trope that's been done quite a lot now (childhood toy/show/experience gone wrong), but it still works well. Great animation and voice acting on the cartoon characters, including the Doctor and the Nurse when they as they went from 2D out to 4th wall-busting characters.
A thought occurred to me while watching - right now the BBC is partnered with Disney. If they had partnered with HBO instead like they have on other dramas... we would have had an episode full of bugs bunny and "What's up doc", a la Space Jam. I'm not sure if that would have been better or worse. :)
Breaking the 4th wall and going meta can be difficult, but I think it paid off. The "real" fans poking fun at the show's nonsense was self aware which helps. All the fans saying "Blink", an episode the Doctor was hardly even in, was hilarious.
I am glad they did keep follow on with Belinda really wanting to go home and not mess around in an abandoned building for at least one more episode.
I still have no clue what's going on with the larger plot about Mrs Flood.