[quote="Nick Sleet"]Along the lines of avoiding confusion, what is the convention for PCs as to changing costumes?[/quote]
Speaking only for myself, I change costumes all the time in every larp I play. I don't even stick with a color theme, like many PCs do. I love pretty, pretty clothes and refuse to be confined to just one outfit

Granted, I generally go with a style or theme for each character -- my Madrigal character usually dresses in fancy jackets or vests and wears a floppy hat. My LE character wore a skirt, corset, blouse and cropped jacket of some sort. That worked in those games, but I'm not sure it'll work here.
Like you, my OR character is going to need different outfits for different occasions -- business suits, stealthy clothes, a little black dress (what? It's armor...social armor), etc. Unlike NPCs, we aren't jumping between different characters, so I have confidence that people will know we're playing the same PC. Mind you, if you end up playing a new PC, you should go with markedly different costuming to avoid confusion.
[b]tl;dr[/b] -- WEAR ALL THE CLOTHING!

“Men occasionally stumble over the truth, but most of them pick themselves up and hurry off as if nothing ever happened.”
― Winston Churchill