@Ravingdoll: I saw this
and thought of the coat. The dress could be in a toning plain colour.
That fabric is gorgeous, but I would use it (or something similar) for the dress and pick up on the mustard in the roses for the coat.
How exciting Dolly, just the sort of thing I would love to attend. I do like a good bit of dressing up! I personally would steer clear of mustard and yellow together, to much of a muchness and probably tricky to match, I would go for a contrast colour.