I was going to propose the forward/backward approach rather than direction=anti-clockwise and that only the loop back has the new relation rather than the whole loop.
Presumably the people who have done some mapping already and Andy (I guess) who does OpenCycleMap will have an opinion on this too.
I was also going to copy your post on the direction of relations on to the Wiki!
Best way is just to talk about it. This is one place; the talk-gb mailing list is another, and probably the most relevant to the National Byway. The IRC channel is good too.
I think you’re probably right (and I’m wrong) about using forward/backward so suggest you just go ahead and add it.