Thanks - I understand that it was a mixture of 47/6s and Intercity liveried 37/4s and 37/5s for Inverness, and then 37/4s to Fort William?
37/0s or 37/5s were used in pairs on the Inverness and Aberdeen sleepers from May 1992, in combination with generator vans converted from mark 1 BGs through to around the end of 1994. There were ultimately three 37/0s and four 37/5s painted in Intercity 'Swallow' livery for these duties, though the locos that worked the services were drawn from a larger pool than just those seven.
Prior to this, from July 1991 Inverness had a pool of seven class 47s, numbered 47671 - 677, with a higher ETS rating to work the sleepers and the daytime 'Clansman'. The pairs of 37s and generator vans were subsequently replaced by RES 47/7s from 1995.
37/4s were used on the Fort William sleeper from their introduction in August 1985 until replaced by class 67s in June 2006.
BR withdrew the seated portion from the Scottish sleepers in May 1992. Prior to this, a standard formation of the Inverness sleeper would be:
Mark 2 TSO-BSO (Seated section) - 3 SLE/SLEP - Mark 2 Lounge Car - 5-6 SLE/SLEP - 3-4 Motorail GUVs
Subsequently, the TSO and BSO no longer featured, and the train would instead include a Mark 1 BG as brake vehicle (At the opposite end of the train to the generator van)
And the Fort William train would be formed:
Mark 2D BSO-TSO (Seated section) - 2 SLE/SLEP - 2-3 Motorail GUVs
Subsequently, the TSO and BSO would be replaced by a Mark 1 BG and Mark 2E FO modified to include a trolley space.
Stagecoach Rail entered into an arrangement from May 1992 to provide seated accommodation on the Aberdeen sleeper. This wasn't successful, and the specially painted coaches were reliveried back into Intercity livery after November 1992, though continued to operate with seating reserved through Stagecoach until October 1993. A typical Aberdeen formation at this time would be:
2 Mark 2 TSO (Seated section) - 3 SLE/SLEP - Mark 2 Lounge Car - 4 SLE/SLEP - Mk1 BG - 3 Motorail GUVs
Some info on the short-lived Stagecoach operation:
The three way split at Edinburgh became possible following the withdrawal of Motorail in May 1995, and was at least partly an attempt to reduce the operating costs of the Fort William sleeper, which had also been under threat of withdrawal.