Scottish Wildcat - similar case to the margay, however you have slightly better chance of seeing these as they do like to sleep in the branches of trees and can sometimes be seen doing so.
There should be no problem seeing the wildcats - they're not as secretive as all that. Margay needs a little luck but far from impossible.
My last visit was about 3 hours as well - but I'd allow a little for a first visit, particularly if not accompanied by a zoo nerd who knows where they're going.