I think you may have suffered in your enjoyment of this episode from having thought too long and hard about the series

Oh I know. Even as I wrote this I was anticipating another phone call with my mum in which she calls me a grumpy old Who fan incapable of enjoying anything any more. Though, in this case, I think the core of the problem was my Buffy fannishness and, in particular, the comparison of Turn Left and The Wish which I think is a much, much better version of the same idea.