5 Dawson Street, Manchester
A very helpful chap at Manchester City Council, called Donovan, drew the boundary of St John's Ward (which ceased to exist in 1949) onto a modern map from a description he had, scanned it and sent it to me... and that allowed me to confirm that the Dawson Street that still exists in Manchester, is the same Dawson Street that my great grandparents lived on.
Dawson Street (indicated by the green arrow) is just in Manchester; the border between Manchester and Salford being the River Irwell, visible although not labelled on the map.
I actually work quite close to this - where the letter "d" is on Trafford Road on almost the left edge of the map.
I have since also managed to view a map of this area on a map from 1896. Not very good detail, but it allows you to see some of the changes in streets. Next step is to get down there and take a photograph of what currently occupies the plot of 5 Dawson Street.