Hi all. I’m the author of http://ridgewaydouble.net/ and the route as posted on that site. The route is (to my best knowledge) 100% legal, which was one of the most important considerations when I was putting it together. There are some sections in the east that may be marked as footpath on maps, but on the ground they are permissive tracks open to bicycles (e.g. National Trust).
The “official” Ridgeway transitions frequently from bridleway to footpath to road, and another aim I had was to stick as close as possible to the real historic Ridgeway whilst remaining legal for bikes. You could of course choose any number of alternate sections here and there if you wanted to mix it up, but I think the route as it is pretty much achieves these aims.
Taps do tend to come and go from an operational point of view. As has been mentioned, some are directly on the side of the trail, some slightly off. There are loads though, so there’s generally another one not too far away if one is out of commission.
Whilst the Ridgeway isn’t the most technical of trails :-), imho as an introduction into longer rides/ITT/multi day riding in the south of England its a nice easy place to start. Lots of places to bivy along the route. Personally I like the stretch a little way after Barbury Castle, some copses with nice views over there.
Cheers. Mark