What a mouthful.
With the hint that the COMBELLACKs may have become CHARLES, and the now knowledge, that the Military records on ancestry labelled as 1914-1922 actually also include earlier service records, I searched them for CHARLES instead of COMBELLACK.
Up popped one Henry CHARLES, of Devonport, born abt 1866, so I read his record.
He enlisted on the same day as Edmund John CHIVERS, for the same Corps.
Next of kin given as father Nicholas of Plymouth, crossed out and "wife Fanny with him" written in.
Fanny later identiifed as the Fanny Grace JEWELL, whom he married in 1890 at Mutley Wesleyan Chapel, Plymouth.
I believe this is Charles Henry COMBELLACK, and the C H CHARLES witness to the marriage of Edmund John CHIVERS and Annie CHARLES.
Just as well he only alternated between surnames beginning with C as he had a tattoo H C on his arm.