I have no direct answer to your queries, although am very interested to learn that there were more Penhallurick's in WW1. The point of my reply is thus, my Great Grandfather was a later casualty of WW1. The story goes that he was gas bombed during the war, not severely enough to outright kill him, but did so some 16 years later through lung problems. He died on the 11/11/36.
If you would like any futher information about this. I can supply it. Just email. Also I will try to find out information on the names you listed.