I think that you and your friends are doing an excellent job. Unfortunately in the early 60's it seemed to be the fashion that having been through Hethrington's Cross Cut, down first Sun Vein and Smallcleugh Sun Vein to the ballroom, then the explorers, just had to leave their name there.
I had even been told of someone who took a ladder into the flat, so that his signature was higher than anyone else's!
If there are any mitigating circumstances, it could only be that these graffiti merchants are following a long tradition as anyone who has been in the Hudgill Cavern knows only too well!