I know I'm not the person you'd expect to reply, but our group has been compiling a photographic index of all the stones in Mt. Pleasant. We're about 2/3 of the way done at this point, and I have a bit of information for you.
I have a stone for John and Lilian Quirk's son, but not yet for the two of them themselves. It's probably here somewhere, but we haven't photographed it yet. The photo is attached (it's not online yet, but it will be at the next update.) I also have two more Quirks in MP if you're interested (who died much more recently.) And yes, Mount Pleasant is in Middlesex, in the city of London, ON.
Check out MP as it goes online:http://cemetery.canadagenweb.org/ON/ONM12701/