Did you find this, Kate? A search on Denholm looks potentially fruitful.
Register of interments in the Greyfriars buryingground, Edinburgh, 1658-1700
And otherwise, some of these perhaps.
(Dreghorne OR Dreghorn) (Cuthbert OR Cudbert) (Denholm OR Denholme) "David Denholm" “Alexander Tait"
I'm sure some of that will be repetitive of what you already have, but you might spot something.
EDIT: Well, if nothing else, the Greyfriars book gives a good number of name variations to look for!