UK, England specifically.
Where do I start? I've spoken to cheese-eating surrender monkeys French people, racist gun-toting fatties Americans, blonde Viking metalheads Swedish people and communist maths savants people from China, and they all seem to have a different preconception.
It's probably because, generally speaking, the English tend to put it about a bit. We did the whole imperial thing a while ago and that was really the last of the great empires. And these days a lot of what I would term 'working class' Brits go abroad a few times a year (don't ask me how they afford it) and seem to pass their time in places like Marbella and Tenerif, where they drink heavily, occupy prison cells and generally piss off the locals.
So a lot of other European countries get the impression that everyone in Britain is like that. Or they subscribe to the American preconception that we're all either twinkly-eyed cockneys or snooty aristocrats. A Chinese student I got to know last year was actually more clued-up on British current affairs than she was Chinese ones, but she seemed to think that British people lived in Middle-earth and did nothing but take afternoon tea and fall in love in various Austen, Brontë, Hardy, Wilde, Keats and, to a lesser extent, Byron inspired ways.
A lot of this is actually pretty close to the truth. Binge drinking is a massive problem in Britain, as is anti-social behaviour and unemployment. The blame for this gets passed around a lot, but for my money it's the fault of a poor attitude to parenting and a strange culture of believing that you are owed something by society.
Anyway, those of us who don't destroy our internal organs and have them rebuilt at the expense of the taxpayer every night tend to be quite calm and sensible. We're generally quite awkward when it comes to our emotions, either failing to experience them at all or becoming incredibly defensive and secretive about them. Manners aren't as important in Britain as my Chinese friend thought, but there are certain unspoken rules of general conduct that can be difficult for foreigners to grasp, about things like how to behave in queues and which subjects are off limits in polite conversation.
Of all the symptoms of being English I think snobbery is the one I exhibit most. Could you not tell? I'm utterly hopeless when it comes to romance and I do speak with a BBC accent. So as an Englishman I am quite stereotypical.
I say Englishman rather than Brit because the obese wasteland of frozen doom Scotland, the mountain of woolly humping Wales and the drunken sea Ireland have entire landscapes of social conventions and eccentricities of their own. Don't lump us all in together, we're a United Kingdom, not a single population.