Donald,
Not wishing to speak for all of us on this side of the pond, (Any one can jump in here) but if you mean double-hooks like in your Silver Ghost; I haven't seen any patterns or anyone using a double-hook fly. But I fish in rivers off Lake (Loch) Erie. Maybe someone on the West or East coasts will reply.

I was trying to find an article I had read about historical patterns to post (link) here, but could not find. It was about Stealhead patterns from the '50's that had a double-hook. But the hook was not side by side, but in a straight line on the same shaft about 37 to 50mm (1 1/2 to 2 inches) seperation. And even for that type of pattern I too am having difficulty finding an example. Or, for that matter, that type of hook in production.

By the way, fantastic web-site. I forgot I already had it saved in my favorite web-site.