Barrow is an interesting one, and I wouldnt have thought Nottingham to Glasgow was long enough to be a sleeper unless it was a roundabout route.
It was the final hurrah of what had been the 21.xx St Pancras - Glasgow sleeper. In order to do away with Sleeper servicing at Cricklewood, it was for a period in the early 70s diverted via Mkt Harboro and Northampton into Euston - where the stock was serviced with other sleepers at ... no sure, Wembley, I suppose.
EDIT - I now see 30907 had beaten me to it on this one.
To save yet more running, I think the ordinary stock reverted to running St Pancras-Nottingham, sleepers attached c midnight, and off via Derby to Scotland.
.. Another anomaly was the sleeper which was the only passenger train on the line from Market Harborough to Northampton and on to Euston running in only one direction but justified showing the route on the BR all-systems map.
As I remember, it ran in both directions.
I caught the Nottingham-Glasgow sleeper sometime mid-week back in 1974 - well, the seated portion. The sleeping cars were ready in the bay which faces Lincoln, the passenger train arrived from Leicester, not sure if it had started at StPancras, the loco was detached, backed onto the sleeping car and shunted it onto the passenger coaches which then reversed direction and headed off to Glasgow, via the S&C and GSWR as already mentioned. I know I was able to stretch out in a seating compartment to myself so I don't think there can have been many passengers
Had it already been cut back to Nottingham by 1974?
I must have caught it one night from Derby in 1973, autumn. I got a berth as I was on duty, going to Carlisle. I think it was still from Euston in that TT.
I also caught the train from Luton in the 60s, and several times in the summer of 68 when I could grab some sleep on a NW Rover ticket by taking the up train from Carlisle (dep approx 00.15 or so) to Skipton, bale out and wait 45 minutes or so till the down train took me back to Citadel, arr 05.45 ish. I think I always got a compartment to lay down in.
A couple of nights doing that and I was pretty groggy during the day, mind
I wonder if it was curtailed at the same time the "Thames-Clyde" was similarly cut-back to run Glasgow-Nottingham?
If it was cut back in the 74 summer TT (as implied above), I think the TC was stll running then as a through train from St Pancras. But it was the same principle, of course - pruning 'odd' services to produce a more standardised timetable.