Ewan wasn't just 'an actor of sorts', Ian: he was an experienced and distinguished actor & playwright with Red Megaphones, Theatre Workshop, &c, & married to T Workshop director Joan Littlewood. Other folksingers/professional·actors were Theo Bikel & some of the Clancys.
Bikel in particular was a master of accents. & don't knock Ewan's Scots accent; he grew up in Salford, but his father came from Stirling & his mother from Auchterarder & theirs was the accent spoken in his home. His Scottish sounded a lot more convincing than Jeannie Robertson's often did after Hamish Henderson got at her.

~M~