*Puts my nitpicking hat on*
This story makes no sense at all. Were the Nazis expecting to lose the war? Why not send their time traveller ten years to the future of Berlin? Assuming they win (which they would assume), the time traveller would probably be greeted by his future self with a dossier including all the information needed to win the war. If they lose, well, it would probably be at least as easy to find someone who can explain why, as it would by travelling to what to him is an enemy country. The only way his plan makes sense is if he is already assuming that future England is still free, and presumes that older German gentlemen would not be out of place in Dover, while at the same time underestimating the lingering hostility.
*nitpicking hat off*
Ok, ok, so it's a fun little historical twist, even if the basic premise is ludicrous. And it brings to mind one of the quotes cited in this week's Podcastle outro - the person from the board who brings up that in times of war, racism is a defense strategy. I guess the moral is - we should never give up our old resentments, as yesterday's enemy may be today's time-traveller.