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Quite a lot of Edwardian houses were built in a style virtually identical to Victorian builds. Ours looks Victorian (and was built in a kind of extension of Victorian affordable housing developments) but is actually 1915. I suspect that a lot of housing developments of the early 20th century basically just took Victorian designs and construction methods (you can see the bricks in my house which were fired in a field shoe instead of a kiln) and replicated them. It took a while for Bauhaus design to filter into UK worker housing.
Search for the street in the 1911 census, if you cannot find it then you are post 1911.
http://search.findmypast.co.uk/streets/street-results-for-1911-census-for-england-and-wales?addressstreet=southwell%20road
Follow that with some style features from the valuation office and the sash windows probably put you into the early 1920s.
http://manuals.voa.gov.uk/corporate/publications/propertydetailsguide/ageCodes.html
I'd probably put 1924 down or ask an owner occupier neighbour if they know.