Hi Chris
I'm stuck as well, but from the names you've given there may well be a connection to my family. I have Duncan Blair x Christian McGlashan 1767 Strachur. Their son (my 4 x g-grandfather) Peter Blair married Catherine McLean, 1800 Dunoon and Kilmun, and another son, Donald, married Catherine McGlashan 1814 Glassary.
Christian McGlashan was a tenant in Ardenslate (owned by Duncan Campbell) in 1800, and Catherine McGlashan was a servant to Duncan Campbell when she married.
Duncan and Christian's other children were Thomas, Dugald and Catherine - and possibly a Mary - all born Strachur.
The dates are all around the same time.