Hi all, and thanks for your interest.
I've ordered a marriage certificate for the lady in question, as she was married in 1916, although by then she's already given birth to my grandfather, whose father I will very probably never trace (yes, this lady is the mystery in our family)...
Her name is Winifred Jones, and I'm waiting for her marriage certificate before I go spending money to confirm what I suspect now...but I think on the 1911 census she's the Winifred Jones who appears as born ca. 1889 in Melksham, living at Semington, Trowbridge, WILTS...
Any more sleuthing very much appreciated!