Hi Graham,
Did you get an answer to this?
I believe the cemetery in the Walton Cantonment, Lahore is located here:
31.496238, 74.397243 (paste this into maps.google.com)
I believe the cemetery is accessible but not certain.
I may be back in Lahore within a few months, I might be able to get photos for you.
I have been documenting various cemeteries in Lahore but did not get to this one.
Kind Regards
Scooter T