Cats -- I recall Kellybray. Didn't King Arthur hold his Court thereabouts? Still, that was probably before your time. I was Admin Officer at the Excelsior Mine Site on Kit Hill. When we were performing official tricks in the tunnel we had to close the Callington-Kellybray Road. That made us really popular --- stopping busloads of shoppers, delaying laundry deliveries, making butchers late, etc, etc.
As to the real 'Coward's Grave', I haven't laid hands on the photo for a while and I've had a fire and 4 moves of house since, so don't hold your breath. I can confirm that it is an official military tombstone in the characteristic British services style and stands in what I was told in 1974 was the 'overflow cemetery'. Does this help?
By all means sing the song. I would like to know that it has finally reached it's birthplace after all these years.