There was a Charlotte Oxenham born in Tiverton in 1841 the duaghter of William and Hannah Harris. William was a sergeant in the DCLI and won the VC in 1857 in the Indian Mutiny. I have a lot of information about him. Hannah then went off to live with a Beer, But there is a puzzle as I don't have a marriage to Charlotte and Thomas Mortimore, Do you have details ? How do you know her name was Oxenham ? On a birth certificate ?