Nintendo of Europe is resposible for all countries in western Europe, not just the United Kingdom. They have the responsibility of translating the game into four diffrent languages (French, German, Spanish and Dutch, I think), and usually try to fit all five languages into one game pack. For a game that is programmed to only output English, this can take some major programming, and the translation time is considerable as well.
That having been said, Europe is the biggest market for video games, as it spans multiple countries. You would think that the smart thing to do would be to have Nintendo of America be responsible for the UK, and just have Nintendo of Europe cover the rest of the western world.
Nintendo could also try releasing games in all languages simultaniously, if they're that worried about importing (Sonic Adventure 2 anyone?). If they came up with the scripts early, they could work on translations while the game is being programmed, and the only diffrence between reigons would be the default language and the reigion lockout code.