Carol
The date was September 1906.
It's anybodies guess what his surname was. Probably whatever he wanted it to be on any particular day! 
Julie
Oh da*n that couldn't be a worse date,it's half way between 1901 and 1911,plenty of time for him to have moved a dozen times between censues.
Just going to look at the 1881 census where Rosie found David with his grandparents to se if there's any clues there.
I notice that he doesn't mention David in his service record,maaybe he didn't know about him till later in life

Carol