Hi Pam,
I would suggest that you get the death cert for the James Sloper that died in 1946, or do you already have this? Who was the informant?
Do you know if he married? There is a possible marriage in Sep Q 1918, Wycombe reg district to Violet Holloway, which I have not investigated (as he is a 3rd cousin 3x removed, so not a close relative), but might be worth you following up. He was living in Buckinghamshire with his parents on the 1901 & 1911 census.
Sue