Rights of way are recorded by the Local Authorities on their definitive maps, or, in some cases, a National Park will supply the information, and Ordnance Survey includes the information provided by the relevant authority (This is only relevant for England and Wales).
If you believe a right of way is in error it may be useful to review this with the relevant authority in the first instance, most of them have a web map available. If changes are required, the authority should inform Ordnance Survey and the data will be updated.