I've just re-watched the entire thing, best thing I've done! I had missed so much the first time, I think I may have a small clue what's going on now.
I love the title sequence! I think it's my favourite part of the show. No, really
And now I've finally realised it changes each episode I get all excited, figuring out what places we'll be visiting (only took me two and a bit seasons to cotton onto that!).