Harry Potter and the Goblet of Fire - North or South?
When Dumbledore is announcing the Durmstrang students, he says that they are 'friends from the north'. Durmstrang is in Bulgaria, Hogwarts is in the U.K. Bulgaria is south of the U.K., so how can they be the 'friends from the north'?
the book never says where they are from, and that they wear furs and such so they must be from the North. They ASSUME Durmstrang is Bulgarian because of Krum, but that is not necessarily the case, it could be Russian, based on the accents even in the book.
It never says were they're from. In fact, in the books they mention several times that no one knows were Durmstrang is. Hermione says it must be somewere to the north because of their uniforms. Krum is Bulgarian, but that isn't were Durmstrang is located.
I agree with the other two comments; the "slip-up" here is the OP's assumption that Durmstrang "must" be in Bulgaria simply because ONE of its students is of that nationality. By that "logic" Hogwarts is in India (that's where TWO Hogwarts students are from). All that we definitely have to go on regarding Durmstrang's location is Dumbledore's statement, and "the north" could be anywhere in the Northern Hemisphere.