I feel like a jerk for not being able to point you in an actual direction, but somewhere out there, there IS a J&W stranded on an island fic. It even has a photoshopped Fry and Laurie. I believe it's called "The Admirable Jeeves," but I can't say for sure. All I can say is that the title is a play on "The Admirable Chrichton" and that several other of the J&W characters are in the story.