Hi Kevin!
I found a site that tells us a little about the swordsmith, whose name appears on the tang of your sword, Fujiwara Masahiro : http://www.hizento.net/index.php?page=history.
To your blessing, he is a noted smith and this adds greatly to the value of your blade. (Did the person who polished the blade, a Japanese artisan I suspect, have anything to say about the smith or the blade?)
Fujiwara Masahiro was also a teacher and the teacher/s of any famous smith is/are always an important part of their biography. (I'm not sure, however, who he taught that became famous.)
If I read the site correctly, it says your sword was made in either 1628 or 1641.
I love fittings and it is good you retain those from the war, which I presume were with the blade when you aquired it, and the shirasaya (plain wooden scabbard), that would have been returned to you with the blade after its professional polish.
The fittings are very samurai (as opposed to standardised post-1868 modern army variants).
This is a family blade and the owner (the "high ranking" officer you refer to) would have been of samurai heritage. Also, because the blade is that of Fujiwara Masahiro, that heritage would have been prestigious. However, and with regret, we cannot tell. Therefore, the blade must be assessed on its merit alone and the fact it was made by a famous smith. (Also, but to a lesser and seperate extent, it can be assessed on its wartime/samurai fittings). Overall, this is a beautiful sword and well worth the effort of the polish.
The scabbard's combat cover is Imperial Japanese Army. Also, if it came from the British army officer you mention then, most likely, it was surrended to him somewhere in the British theatre, probably Burma. However, this is a wild and silly guess, but a good starting point for glass-of-whisky conjecture.
Thanks again.
Keep well
Satsuma