An expression coined long ago with regard to English people, normally when abroad. Used to great effect by Ikea in a series of commercials released in the United Kingdom, the basic premise of which was that English people should stop being English about their interior design and buy something modern from Ikea.
Perhaps the best of the series featured a scene with a woman in bed, the covers up right to her neckline so all that you could see was her head. The husband enters with his flannel pyjamas on, sits by the bed and switches out the light. We then see nothing but hear the rustle of bed clothes as he gets into bed along with some small 'ooh' and 'ah' noises. Suddenly, silence, broken by the man's voice shouting 'Hell's teeth woman, you're NAKED'
I admit to being guilty of using this phrase years ago whilst living on the Continent. You would often hear English people talking in loud voices in a bar about local customs and habits and how much they disliked them. If angered or embarassed enough for them I would tell them to 'Stop being so English' and enjoy the differences in culture that existed between here and their beloved homeland.
Quite frankly if you don't like the place you know where the airport is.