Hi
Have you obtained copies of their naval records from The National Archives?
Description Name Stamford, Christopher Herbert
Official Number: J11924
Place of Birth: Camberwell, London
Date 17 January 1895
Catalogue reference ADM 188/670
Dept Records of the Admiralty, Naval Forces, Royal Marines, Coastguard, and related bodies
Series Admiralty: Royal Navy Registers of Seamen's Services
Piece 11501-12000
Description Name Stamford, William Gilbert
Official Number: J20617
Place of Birth: Southwark, London
Date 12 November 1896
Catalogue reference ADM 188/688
Dept Records of the Admiralty, Naval Forces, Royal Marines, Coastguard, and related bodies
Series Admiralty: Royal Navy Registers of Seamen's Services
Piece 20501-21000
Description Name Stamford, George Frederick
Official Number: J38186
Place of Birth: Wandsworth, London
Date 15 September 1898
Catalogue reference ADM 188/723
Dept Records of the Admiralty, Naval Forces, Royal Marines, Coastguard, and related bodies
Series Admiralty: Royal Navy Registers of Seamen's Services
Piece 38001-38500
http://www.nationalarchives.gov.uk/documentsonline/power-search.asp?searchType=powersearchChristopher would be to old to be in an orphanage in 1911 and possibly William.
A free search of the 1911 census shows William G Stamford aged 15 in Holborn registration district. He is an household not an institution. There is a George aged 12 in Bermondsey. He also is in an household. Their naval records will tell you when they enlisted.
If none of them were in an orphanage in 1911 without knowing which orphanage or indeed poor law system they entered it will be hard to find which one as London had quite a few.
Regards
Valda