Things have certainly improved a lot. In the 1985 timetable there is an hourly service at xx:45 to Kilmarnock until 16:45. Then there is a 17:30 (through to Carlisle), then nothing until 20:00 (which goes through to Ayr)!
Yes, quite horrendous when you look back at it
I don't remember the 20:00 going to Ayr though
Lastly there is the 22:15 sleeper to Euston (the Glasgow > Euston sleepers with seating accomodation ran this way then: there was a sleeping cars only portion that joined with the Edinburgh > Euston sleeping cars + seats at Carstairs)
The Edinburgh - Euston sleeper was a stand alone, it did not join or split with anything
The other sleeper is the Plymouth, both of which joined and split at Carstairs
Later this changed and the Glasgow was also rerouted via Carstairs
The 20:00 Glasgow - Kilmarnock was then strengthened to a double DMU, arriving back in Glasgow in time for the sleeper
However, passenger numbers were vastly lower than anticipated so it returned to a single DMU
Supplementing this are DMUs from Dumfries into Carlisle at
07:37, 11:37 and 22:37
IIRR the DMUs on the Dumfries shorts were Ayr based ScR units rather than Carlisle based 108s
These were indeed Kingmoor based Class 108 units, there was nothing Scottish DMU based south of Kilmarnock at the time
These DMUs then formed other services to Whitehaven, a rather strange arrangement rather than having through advertised services
Equally, I remember one day where these services were operated by a Class 31 and GSW coaches as a Class 108 was not available