Why not just kill the geologist? (Spoiler)
It seemed to me the premise was badly flawed from the very beginning. If it was so all-important to London to get that geologist out of there before the Germans figured out who he was and he spilled the beans about the landings, the obvious thing would have been to go in and simply kill HIM. Not send in a whole commando and put on that elaborate operation (nurses, ambulance, strippers, etc., etc.) and risk so many agents for just one guy who was badly injured already.
Sure, that would mean killing one of your own, but the whole theme of the film was that they didn't mind doing that if they had to.
Despite it all, I rather enjoyed the movie -- although I think it's basically an attempt to cash in on the success of Pierre Melville's similarly titled L'Armée de l'Ombre (which is excellent) -- but, honestly, it's NOT a very good movie -- despite the presence of a bunch of very appealing actresses.
I always especially enjoy any chance to see Sophie Marceau and Julie Depardieu.