Think I might have solved this one (sort of)!
I checked the British Telephone Directories database on Ancestry for Cumnor in 1955 and found listed an F.J. PAYNE, Engineer of Rockley, Cumnor.
According to FreeBMD, I think this is the Francis J. PAYNE who married Gladys O. GAYTON (Oxford RD) in 1955. (Could the "O" on the death certificate have been misread as "C"?)
I could find no birth record for Gladys, so thought it might be her second marriage and looked for a Gladys marrying a GAYTON, and found ...
1927 (Headington RD) - George F. GAYTON m. Gladys O. PHIPPS
There's your PHIPPS connection! George and Gladys had three children - John F. (1928), Peter M. (1930) and Margaret A. (1939). The first two were registered in Headington RD and the last one in Oxford RD.
Hope this may help!
Pennie