Well... no. I haven't. Though the two charecters do overlap a bit, as "Holmes Last Bow" ends just a bit before World War I, and Hercule Poriot's "The Mysterious Affair at Styles" starts sometime during the war.

Actually, that might be quite fun to write, except the fear of the gratiiuitis French. A small meeting, at least.

And you kinda have to go *la la la* over the bits where they say that Holmes is fictional, but whats a fanfic without the tiny breaks in cannon? = )