Hi Jim,
I'm a bit stuck here, in more than 50yrs of playing with sharp and pointy's I have never seen a Continental briquet type sword with British issue marks or British regimental marks. I do not claim by any manner that such an item is not out there but if it is it must be the proverbial hen's teeth. However hen's teeth do exist, e.g. the sword in this post,
http://www.vikingsword.com/vb/showth...1796+sergeants was confirmed recently by the Royal Armouries as indeed a 1796 pattern nco's sword and it seems the very few examples they have do not have the scabbard, so a scarce item but a known pattern. Privately raised regiments and militia were outfitted by the raiser/s and of course export/commerce was practiced extensively so maybe this is a possibility although I'm not hopeful. Texts and Museums do get things wrong as we all know and in fact looking into your Briquet I delved into the Royal Armouries collections and found a Briquet, museum no IX.1182, tagged as French but it is in fact Swiss as it is described as having a crowned double A which is the Bern Armoury mark so mistakes are still out there. I have attached images of the British sidearms that I know of with brass stirrup hilts.
My Regards,
Norman.