I recommend, 'Watching the English' by Kate Fox: Watching the English: The Hidden Rules of English Behaviour: Amazon.co.uk: Kate Fox: Books
It's so spot on as to be funny. I recommend it to every ex-pat I meet. I used to test it by asking my British colleague next to me at the office questions, I had conversations like this a lot:
'You know that picture you have of you and the Clintons, is it in your downstairs loo?'
'Yeah, how'd you know? Why?'
'I read this chapter that said that Brits would put something like that there because they knew everyone would see it, but it would look like a joke because it was in the loo.'
'Uhhh...Actually that sounds about right....'
It's actually really helped me understand my current home. Of particular interest to any youngish ex-pat is the, also accurate, chapter on dating. It can either help you avoid a bit of trouble and misunderstanding or help you take advantage of the system, depending on which way you'd like to play it (so to speak).
I find, in general, the culture shock in England to be worse than in Japan. Sure, I'm only in Japan for small stretches, and never really 'living' there, but you expect it to be very different. I think many people don't expect the culture of a people who look roughly the same and speak roughly the same to be all that different, so when the misunderstandings do pop up it's like stubbing your toe in the middle of the night. Had you been expecting it, it wouldn't hurt at all - but you weren't expecting it so you're hopping around grabbing your toe yelling expletives.
I also think this is pretty accurate: Stephen Fry on American vs British Comedy - YouTube