And now for something completely inexcusable

While watching And Now for Something Completely Different for the first time in a long while there were a few lines I couldn't quite understand, so I turned on the DVD subtitles.  But they were obviously written by a clueless American:  Oswestry is called "Oswald Street" in How Not to Be Seen and Oliver St John Mollusc is called "Oliver Singen Mollusk" in Upper Class Twit of the Year.  How hard would it have been to check with a real Brit when not sure what was said?  Monty Python fans deserve better.