Tolkien in 1916
I have done research for a display about the experiences of science fiction and fantasy writers during the First World War. The banner display was at Loncon 3, the World Science Fiction Convention in August 2014, one hundred years after the Great War broke out. A record of my research is up on my website Science Fiction and Fantasy Writers in the Great War. The website looks at writers one by one; the banner display looks at their contribution to the War chronologically (each banner covers six months).
Edward James 
Sounds like a fascinating project.
William Hope Hodgson might be a candidate (though another Brit, unfortunately!).
That was really weird: this morning I got an email from my friend Andy Sawyer, who is the librarian of the Science Fiction Foundation Collection at Liverpool University, reminding me to include William Hope Hodgson…! Yes, I know he is another Brit, but increasingly (as I gather more and more material) I think I shall stick to Brits…