"This is the United Kingdom of Britain and Northern Ireland," the Doctor explains, yanking her inside and showing her the ship. "All of it, bolted together and floating in the sky: Starship UK. It's Britain, but metal." Great line! Then it goes sour, once again: "That's not just a ship, that's an idea. That's a whole country! Living and laughing and... shopping, searching the stars for a new home." After this nod to meaningfulness, there's cutesy back-and-forth verging on flirtation about how the number one rule is that they must not, must never, get involved in the affairs of other people or planets. Get it? Because he always does, that's the joke. That's what serves as a joke.
Amy stares at a little crying girl on the screen, down there in the ship, and compares them to wildlife documentarians: "If they see a wounded cub or something, they can't just save it, they've got to keep filming and let it die. That's got to be hard. I don't think I could do that. Don't you find that hard?" She finally looks away from the little crying girl, but of course the Doctor's already gone.
The set, London Market, is pretty remarkable. An intense amount of hustle for what is probably a fairly small area in reality, lots of colors and clothes, all of it lavish and particular. Amy wanders through it realizing she's really in the future: "I've been dead for centuries." The Doctor calls this gloomy, because he doesn't like to think about that, because he doesn't have to think about that, and then asks a bunch of Socratic nonsense to get her to figure out something that we, the viewers, can't be expected to have figured out, which means it's just the Doctor being annoying and unnecessarily dramatic, which is on the script:
"Look at this place. Isn't it wrong? Use your eyes, notice everything. What's wrong with this picture? ...Come on, look around you. Actually look...." It goes on for awhile. "Life on a giant starship, back to basics. Bicycles, washing lines, wind-up street lamps. But look closer. Secrets and shadows, lives led in fear. Society bent out of shape, on the brink of collapse. A police state." Oh, right, now that you mention it I see all kinds of "secrets and shadows." Thanks for telling me, rather than showing me, what he is talking about.
Then, just to cram even more mystery and wonder into the story for no reason whatsoever, he snatches somebody's water glass off the table and puts it on the floor and stares at it for awhile, and instead of slapping the shit out of him for being dorky and annoying, the people sit there while he makes a lame joke about how he's looking for an "escaped fish," and then wanders away. The fact that they don't give him a wedgie or toss him out of an airlock for acting like a jackass, that may well be a sign of a police state too.