To clarify, only one of the horns has been carbon dated. The dates you quote are correct. This of course does not mean that the dance is that old, only that at least one of the horns is.

The village website has this statement:
"The Abbots Bromley Horn Dance, performed at the Barthelmy Fair in August 1226, is one of the few ritual rural customs to survive the passage of time."
There is no evidence at all that this date is correct - it's a piece of fanciful make believe.

Derek