One thing you very quickly notice about life in the UK is the difference in keyboards. Although I've been here for over a month now, I still don't remember that the @ symbol is down by the semicolon instead of up above 2 (that's where you'll find the double quotation mark).
The other change I notice is that the # symbol has its own dedicated key instead of being above 3, which is where the £ hangs out (which is fairly amusing if you think about how our American friends refer to # as "pound"). This is obviously sensible, though I do wonder why they simply didn't replace $ with £ and move the former to be a secondary key, like the Euro symbol.
But I really don't understand the logic behind @ and ". My usual answerer of tricky questions, Wikipedia, is exceedingly knowledgeable about the differences between the British keyboard and what I would call 'the normal one', but is surprisingly quiet about the reasons behind the key-switcheroo.
I suspect this will remain a mystery unless I decide to fork out £32 for a copy of BS 4822, but I would love it if somebody out there could tell me why the @ symbol is in a different place on the British keyboard?