Progress report. Ada's marriage certificate (to Charles Francis Bullard Birchall in 1889) says Ada (no middle name)Double, age 20, father Joseph Double dec'd, occ Baker, all correct facts. So far then, apart from the appearance of the name Edgcumbe, no connections made. She divorced him in 1902 (rare occurrence), I'm waiting to hear from TNA how much it will be to copy her petition papers, may be a clue there.
Incidentally, after a second marriage, she died in 1935, leaving a sum worth £113,667.49 to her son from marriage one!
More later perhaps.
MaxD