I have a marriage certificate of my grandparents, Stanley Semmens (Father William James Semmens, Miner) and Florence Mary Trewhella (Father : Christopher Trewhella, Farmer), dated 31 March 1920. Witnesses : William Trewhella and Anne Phillipa Trewhella. Place : S.Uny Lelant.
I cannot trace them anywhere on the Ancestry databases.
I also have a family bible with the names John Thomas Gilbert Semmens mentioned.