For details on the distinguished career of Dr Cecil Armstrong Gibbs, see Stephen Banfield's profile of Gibbs in Grove 6 VII:35-38.
Reconstructing the steps by which a researcher arrives at new information is usually instructive:
I found a citation to the Gibbs "Ephelia" setting in the World database at the NYPL Research Facility. I then requested a copy of the published score from the Sibley Music Library, Eastman School of Music, Rochester, NY. I then contacted the setting's publisher, Boosey & Hawkes, London, for the mailing address of a Gibbs relative. The publisher put me in touch with Gibbs's daughter, Mrs E. Ann Rust of Gloucestershire, England, who, recognizing the name "Ephelia," directed me to soprano Georgina Colwell, Hersham, Surrey, who sent me inscribed copies of her recent CDs, which include her performance of Gibbs's setting. Colwell wishes to be considered an enthusiastic member of the reconstructive wing of the Ephelia debate. See my note on Colwell, Restoration (Fall, 1997), 114.