20121 has now been repainted into training livery.

Stagecoach on Teesside 20121 (P121 XCN) by Tony Kuy, on Flickr

And good news - 21037 is now the only withdrawn vehicle in Stockton yard.
Stagecoach on Teesside 21037 (L37 HHN) by Tony Kuy, on Flickr
The piece of paper in the windscreen and on the door reads: "Sold for Preservation - Not To Be Removed!"