The 'Pav-a-lova' thread got me twitching about this again. It really annoys me because I don't understand why we do it, but am happy to be put right by a know all wiser person than me.
So why do we feel the need to have a British translation for the name of a foreign country or city? What's would have been wrong with calling Spain Espana or Munich Munchen? To me its an utter nonsense, you are not translating from an existing known word in one language to an existing known word in another language - someone has gone to the trouble of making up a completely new and meaningless word loosely based on a word that cannot be translated as it is a naming noun.
Equally mad in reverse - other countries inventing 'names' for the United Kingdom.