-Make a two fingered V for victory sign at someone with your knuckles facing them. This is an extremely insulting gesture.
-Ask personal or intimate questions, such as: "How much money do you earn?" "Why aren't you married?" or "What is your age?" The English are extremely private people and this type of questioning, however well-meant, is unlikely to indear you to your hosts.
-Pass wind in public--through any bodily orifice!
-Speak when your mouth is full of food.
-Call England "quaint."
-Greet people with a kiss when you have never met them before (this type of behaviour is normally reserved for close friends and relatives).
-Discuss politics or religion! Whilst not exactly taboo subjects, the English regard their political and religious beliefs as their own business--it really is far safer to avoid such talk, if not completely, then at least until you know your hosts a little better.
http://englishculture.about.com/culture/englishculture
