I used to live in Carlisle Street, which led directly off Norman Street and well remember Mrs. Polly Beaman (although I didn't know her name was Polly) who kept the little shop. As a young girl I would go to the shop for my mother for various items. As you say, she was always very helpful - people would have a 'slate' which they would pay off as and when they could.
I thought she was a lovely old lady and remember her telling me about her only son who was killed on armistice day at the end of the 1st World War. On the Absent Voters List for 1918 a Joseph Beeman is listed as living at 30 Norman Street - and I believe this was her son.
I also remember seeing your grandmother at the shop.
Although I was only very young I have a distinct recollection of Mrs. Beaman although, unfortunately, I don't have any photographs of Norman Street. However, if you go on the Winson Green and Brookfields site and go into the Winson Green Section 'Streets', under Carlisle Street you will find a photograph of the Cottage of Content Public House which was on the corner of Norman Street and Carlisle Street looking up Norman Street towards Winson Green Road.
I hope you find this useful.