Hi, thank you for all the suggestions and advice, it's very much appreciated. I've been looking right across the net this evening for fabrics, including handkerchiefs, napkins and Christmas fabric and found several that I like. These are two that I've narrowed down.
bearisgray, that's what i was thinking, and maybe add a little ruffle of lace/fabric under the underskirt to lift it out slightly.
But, the more I look at the fabrics, I'm a little unsure of having a patterned underskirt and dress. Instead, I'm thinking of having the dress plain and edging it with beads and trim, and having the pattern on the underskirt.