I haven't come across a Churchill named 'The Saint' but am almost certain I've seen a photo of a Sherman so named and caryingthe the stick man logo.
I'm trawling through my reference books but all I've come up with so far is an illustration in Tanks of World War II by Chris Ellis (ISBN 1-85152-725-7)of a Sherman M4A2 with the stick man on the side. I suspect this illustration is derived from a photo as the associated caption goe into some details saying that it took part in the Anzio landings and belonged to a Canadian regiment (wd number given is T224550 - and the illustration shows it being a member of B squadron).
Do any of these details make any sense? Are you sure your grandfather served in a Churchill in North Africa? This would imply he served with either: North Irish Horse, 51 RTR, 142 RAC, 12 RTR, 48 RTR or 145 RAC. Any extra details you can supply will be of great help.
If you happed to come across the photo please keep us informed.