Thank you so much, Dinosaur,for spending so much time posting all this info; I'm sure you are putting a lot of us out of our misery, because we all seem to have got caught up in this story!
I did find Frederick Turner only last night, but as I am a bit of a novice, I wasn't sure it was him - particularly because in the 1871 Maria is referred to as his sister. For the rest of you, the entries are thus:
1861 census at the Military Barracks, Shoeburyness, Frederick Turner, 25, Sergeant, Royal Artillery, b. Oxford and Elizabeth Turner, 25, b. Gibraltar.
1871 census shows them at Elswick, Northumberland: Frederick Turner, widower,36, Volunteer Adjutant, b. Oxford with Frederick (son) 8, b. Essex, Shoeburyness; Maria (sister), 40, b. Oxford, Woodstock and Frances (niece), 18, b. Berks, Reading.
In 1891 Frederick, 55, Retired Officer, Royal Artillery, is with wife Frances F, 35, b. Reading, and various children.
The entry for Maria had confused me somewhat because I knew Frederick didn't have a sister called Maria, so thanks for clarifying that one - and many other queries - Dinosaur!
Regards
Greensleeves