Not technically or officially Europe anymore (that's just stupid--err, sorry for the political content), but if you're headed to London,
Aperture UK stocks quite a bit of vintage Nikon gear, as does
Fixation--they're the top repair place in London, but also sell new and used stuff. And then of course there is the great grandaddy of all Nikon stores in London,
Grays of Westminster, where you'll be served by proper English gentlemen wearing ties. Prices to match.
I've shopped all three, and had very good experiences.