Well, new Who has made quite a bit of use of the idea of parallel universes, so that certainly allows for the possibility that our universe is parallel to the Doctor's. But to be honest, I think I prefer to imagine they're the same universe, so that I can pretend I could stumble across the TARDIS at any moment. Yes, I take your point that as things stand, I would either already know what it was and who to expect inside it, or have to instantly forget everything I know about the TV series and its spin-off merchandise in that moment. But the fundamental appeal of Doctor Who to me is the same as Narnia or The Wizard of Oz - that any ordinary person could make the same sort of journey as the characters in the story from the everyday world into a fantasy world of excitement and adventure, if only they can find the right portal. For that reason, I'm pretty heavily invested in seeing the everyday world when it is portrayed in the series as being the same as ours.