That whole "Zulu" thing goes back to the 200th Anniversary of Monmouth in 1978. They showed the movie one night outdoors. The Americans started chanting it the next day when opposite the 23rd Welsh Fusiliers. And it became part of reenacting lore.
Fremantle never wore a uniform while in the US/CS. In fact, he wore hunting clothes which at least once he felt to be too shabby for a moderately formal dinner party to which he'd been invited. De Joinville wore a Federal uniform as a member of Mac's staff. I believe there's a photo of von Zepplin (sp?) wearing civilian clothing in the field. Dare I say, old thing, that the British togs are right out. Reenacting officers can be very touchy about young reenactors sporting rank. Reenacting is like the "old army;" it takes years sometimes to make junior rank. We also attatch outsized importance to rank because of our relatively small numbers. We also tend to bring a bit of modern army "officers are scarce and NCOs are highly trained" philosophy to the table. That may go a ways to explain your cool reception. Some of those folks were probably bristling at the thought that the circus had just come to town and might want to take over. (No offense intended.)
Pine River Boys, Co I, 7th Wisconsin
"We're... Christians, what read the Bible and foller what it says about lovin' your enemies and carin' for them what despitefully use you -- that is, after you've downed 'em good and hard."
-Si Klegg and His Pard Shorty