Yesterday we were in Melton Mowbray, and we thought we'd drive back via the Wreake Valley, partly because it's lovely, partly because I used to live in Rearsby and haven't seen the place in years.
I was slightly surprised to find that the road along the west side of the valley has been designated, and fully signed, as NCN 48 (the promising-sounding Fosse2 project) - so our old house now has an NCN route past it. (The next place we lived is about half a mile from NCN 63; then the next is about a mile from the National Byway; and our boat is moored a few hundred yards from NCN 54, too. Just need to get that route through Charlbury...)
I was even more surprised to return home, check on the (usually very comprehensive) Sustrans website, and find that the route is still marked as "proposed" there. So in one small way, OSM's NCN mapping is now more up-to-date than the official one!