The plumbers shop could have been below.. there are still many of the old buildings along London road (although many are gone) and most are shops but at the side of each shop door is another door leading into the 'close' which is the entrance from the street.
Some will just have stairs inside that take you up to each landing which peoples 'front doors' are whilst others will have hallway and possibly a couple of doors leading to peoples homes but also with stairs and homes upstairs. The lower floor homes would only have had windows at the back.
My own Grandpa was raised in the High Street in Glasgow and this is the same, (still standing) it's a shop at ground level with an entrance to the close next to it which leads to the homes above it
