All right, you are writing a historic romance set in late Victorian London. Middle class girl is in love with poor boy but dad wants her to marry wealthy guy. Now, exactly where does everyone live?
In 1898-99 Charles Booth did a survey of London showing exactly where all the economic classes lived. It divided London into seven classes, from the very wealthy to the worst slums. Below the 1899 map is a modern map so you can compare the two. (Modern map does not show economic state, just what is there now.)
Click on the little map on the left to pinpoint a particular neighborhood. You may not be able to read street names easily, but it does give enough reference to find it on a modern map.
Now you don't have to guess, or steal a street out of a Victorian novel everyone else has used. Or worse go by what is there today. Some of those posh neighborhoods are no longer posh, and some neighborhoods have gone the opposite direction!
Link to: Booth Poverty Map & Modern Map