Camden Town. The problem is the tents are slowly being bought up and replaced by corporate stores, from what I've heard (I was there a few years ago before that fire and that's at least what people told me). MLB, as for using oyster cards when you leave, most places will have gates that won't open until you use your card. That makes it pretty convenient to figure which is which. The only confusing one is the DLR. I'm honestly not sure what the rule is for that thing, since there aren't any doors and the thing you have to use wasn't always obvious for a tourist like me. But, unless you're planning on seeing the Docklands Museum (which is pretty cool) or Canary Wharf, I don't think there's any reason to worry about that.