The fluer de lis really does throw people off as it is typically regarded as strictly French. Actually the three fluer de lis existed in the Royal arms of England until 1801. ….and as such did represent France in the heraldic circumstances that go back to Edward III.
It seems to have a lot broader connotations of course. Regarding the fluer de lis you mentioned as a makers mark in England, I dont think it was a makers mark but possibly a quality type mark. I believe there was a street named flier de lis street somewhere in England where blades were sold in bundles to 'sword slippers' but cannot recall more, but it was about mid 18th c. It might have been in Aylward or one of the references amidst the Shotley Bridge research.
You know it'll drive me nuts til I find it!
I think there was one or more of these blades in "Swords of Culloden". As you noted earlier though, there were some German smiths who used fluer de lis but these may have alluded to these used with Toledo blades in some cases.