Denis, I did the following as I was expecting hassles with German customs (anything just remotely looking like a weapon gets these guys highly agitated) when someone sens sends a sword from abroad:
I formulated a nice letter in German to be attached to the outside of the package marked "for customs attention" in BIG letters. In the letter I very politely described the sword in detail, its historical value and age as well as asking them to only please handle it with great care, wearing soft gloves and not to touch the blade under any circumstances.
I also stated my cell phone number asking them nicely to phone me if there are question. The result: they did read the letter, never opened the package themselves, but asked me to open it when I picked it at customs to inspect it (they never wanted to touch it).
Maybe this would help with customs in other European countries as well; these guys obviously don't have the knowledge to handle Nihonto ( and to be honest, how could they?). Anyway, we have a small local customs office, and by now they know me and are interested if packages arrive from Japan :D
Andreas W