I first travelled to Scotland in 1979, other than a two-week school hiking trip in 1974, and I worked in Glasgow Control from 1984 to 1987. By that time the use of 27s on the West Highland Line was quite rare, since 37s handled all the passenger trains and most of the freight. The Edinburgh - Dundee circuit was pretty much solid class 27 (there was a single class 47 diagram), and the introduction of the "Arbroath"* diagram added to the variety. 27s were also common substitutes on the G&SW route, and to Stranraer - sometimes in pairs.
In later years the standard of maintenance and the lack of overhauls meant the class 27 fleet became synonymous with unreliability and lateness. Some particular locos were especially poor, and wherever possible were confined to light work around Millerhill, or local trips from Ayr. The 27s were always entertaining, and a central character in the Scottish scene of the 80s.
* If my memory serves me correctly, the Arbroath diagram involved a set starting at Dundee, then working Dundee - Edinburgh, Edinburgh - Perth, Perth - Glasgow Queen Street, 16:03 Glasgow Queen Street - Arbroath, then 18:50 Arbroath to Dundee. I can't recall what the diagrammed traction was, but 27s, 37s and 47s all turned up on it from time to time. Once when I was on early shift I was left a note that I had to move a 27 from Perth to Dundee for weekend engineering work, but there were no spare drivers available to do it. There was a 27 on the Arbroath diagram that day, so during the layover at Perth I got them to multi it up with the spare 27, and it ran as a pair of 27s Perth - Queen St - Arbroath - Dundee. I clocked them at over 100 mph approaching Carnoustie on the Queen St - Arbroath leg!