OH MY GOD YOU LOOK GREAT IN IT AS-IS TELL HIM TO CHILL!!!
Sorry, had to get that out. I can only imagine your frustration at this point.
Elle, you've been pretty angst-y about spending lots of time with inlaws/other wedding guests, right? And some of this is expressing itself in your desire to wear the "right thing," and his nixing dresses he things are too this/that/the other, yes?
Why do I have the feeling he's projecting similar fears/anxieties onto your poor clothing?!
Remind him if nothing else, Brits do love their eccentrics. Even if you're that over-the-top, not-our-kind-dear American it will be all right in the end.
Now tell him not to say another word aside from "Beautiful" [etc] and to start doting on you know. You two need to be blissful not bickering in the midst of all those strangers and family members!