Hello Liz,
Unfortunately your uncle's date of death was outwith the 'criteria' for both CWGC and SNWM for inclusion in their databases.
I suggest you contact East Renfrewshire Council, give them his details and they should then be able to tell you the Section and Lair Number in which he's buried. (They may also tell you who else, if anyone, is buried in the same lair.)
See:
http://www.eastrenfrewshire.gov.uk/index.aspx?articleid=1718Once you get the details, anyone familiar with Cathcart would have a much easier job in trying to find the grave.
Good Luck!
Anne
