I've probably caught more mullet on a chartreuese / white bead eye clouser than any other fly.....all total about 4. With that being said, I know a fellow that takes a dry fly hook and ties a piece of white yarn, similar to an egg pattern, some with and some with out sparkle. Then he'll chum up the mullet with some bread and crackers. when they gather en masse, he'll slip the fly in. One drawback, hardheads will show up in with the mullet. That can create a mess.

Also, there are a couple of forums on UK sights (that I have stumbled across) that direct their discussion to fishing for mullet.

Tight lines, Chris