Don't think the idea ever progressed beyond the drawing board.
I heard that GNER was once trying to convert some sleeper Mk. 3s to day coaches, and apparently they had oval windows?
Anybody have any pics or information on this?
If I remember correctly and from the artists impressions at the time the plan was to just leave the 4 small windows on what was the corridor side of the sleeper as any attempt to open out or cut new window apertures would've weakened the body structure so the plan was to have the seats angled on this side in a single seat configuration and 2+2 seating on the other side.
I have seen a picture of one with various styled windows including ovals. Were they not MKIII SLEP conversions?
There was one vehicle converted by Porterbrook as a trial (10661), but it wasn't specifically for GNER, although it did gain GNER colours as a livery trial later. There is a pic at https://c1.staticflickr.com/7/6162/6201173616_76efaac58f_b.jpg
That one perhaps?
https://www.flickr.com/photos/manofyorkshire/8002550450