I've had sucess on black stonefly nymphs, there was an article in the Trout & Salmon a few years ago. When we meet up on the Avon I'll bring a couple along. Most of the guides at Rynda have a really good selection of their own flies, especially Gena's creations!
Re "Mutt's Nut's", don't quote me but I think it was oringially tied by a welshman fishing at Kharlovka/E.Litsa. I think you'll find something in the archive fishing reports.