Sorry I was wrong
I have thought all along the the Mures of Cowden were referring to Coodham near Kilmarnock. It is Cowden near Neilston in Renfrew. The Mures also held Glanderston near Neilston.
This shatters my theory that the Mures were in similar areas to the Caldwells. The Mures cerainly had a lot of property but it looks like Rowallan was the only Ayrshire outpost. (Polkelly is in Ayrshire also).
Saw a picture of Cowdenhall on the web - it was a reasonable sized "pile".
One of the early Caldwell's in Kilmarnock was in the service of Montgomery. This would suggest that he came down from the Renfrew area.