thanks for helping everyone - sorry, have been busy again this week - including discussing this with 2 members of Ancestry who have used the pic and the one who originally supplied it.
The mystery is solved - the older lady is, indeed, Bridget (Collins) Brislin - my great-grandmother - and the younger 'Mary' is her granddaughter, Mary-Agnes - who would be one of my mom's first cousins (not sure, yet, if they met - although mom knew her older sister Kate/Catherine).
Now I have that information confirmed, and I know that Bridget died in 1926 then it has to be around then - the 1920's -
The 1911 census has Bridget & Thomas and Martin (my maternal g/father, one of their younger child - they had 7 or 8), then living at 3 Elim Place, 167 Aston Road.
That is also the address on my g/father's army discharge papers in 1919.
So I think it's almost certain that was where the photo was taken - and looking at the set up on the maps available it seems to be a courtyard/back to back type thing - another reason it was demolished ages ago I suppose.
In one map it does show a 'Foundry' opposite - brass I think.
when you enlarge it, it seems to have - to the right of the wording 'Elim Place' - what might be a set of steps/stairs, which might explain the raised up terrace in that photo.