There are 2 Charles William Buckwell, the other one is born 1884 in Sussex and was a Major. I cannot find the man we are after in UK censuses
1896 Oct 2. (RN records) . Not born in UK. Edwin Charles Buckwell apparently married Candida Narduzzi ( from military card). His birth was registered as a Consular Birth in Milan C W H G Buckwell
1915 Enlists in Royal Naval Division. He is a student Naval Engineer. His mother lives in Italy. The assumption is that was where he lived too.
1917 Sep 26. The undermentioned . temp. 2nd Lt. (attd.), are. transferred to Serv. Bns., with seniority from 26 Sept, 1917- West Yorks Reg, C W Buckwell
1919 May 30 . MC Gazetted. T./2nd Lt: Charles William Buckwell, 11th Bn., W. York. R
1921 May 12. Joined ADRIC with service no 1959. Posted to C Coy
1922 Jan 13. Discharged on demobilisation of ADRIC
1930 - 1933 living in Kensington Charles William Gye Buckwell
1939 Register Living at 178 Kirkdale , Lewisham, London,. He is a Foreign Representative
1940 Jul 25 The undermentioned to be Lts, Lt. Charles William Henry Gye BUCKWELL, M.C. (147219).
1947 Apr 29 Intelligence Corps. The undermentioned relinquish their commns.: War Subs. Capt. C. W. H. G. BUCKWELL, M.C. (147219), and to be granted the hon. rank of Major.
He then disappears, presumably back to Europe.