Thank you so much for all this information.
I'm confused about Evelyn Joan as I'm not sure where she fits in, if anywhere, I don't think Flo was her mother. Incidentally there seems to be some confusion about Flo herself, the G R O Indexes have her being named Edith Florence but she was married as Florence Edith and was always known as Flo.
The disabled girl was Irene Elizabeth Kerrison b 1920/MAR Islington; mmn Stribling. Her parents were Flo's eldest brother Albert Henry b 1851 and his wife Elizabeth Bartley Stribling, there was also a son, (another Albert) born 1922. During his war service Albert senior had lost a leg and been left in constant pain which he tried to alleviate by drinking heavily. Elizabeth doesn't seem to be on the 1939 Register and there is a rumour that she just couldn't cope with everything and simply walked out on her family.
From what we hear it sounds as though Flo took on responsibility for disabled Irene in addition to continuing to run her "corner shop". Unsurprisingly this all proved too much and Flo is said to have asked her younger sister, plus her husband, to move to Gravesend to give help. The younger sister was my cousin's mother, Ruby Alice, and we've been trying to establish the timings of these various matters.
We know that Flo and Harry Wrench were married in Southwark 1939/MAR but had arrived in Gravesend by National Registration Day later that year. We have official paperwork (A.R.P. Training Certificate!) for my cousin's father, showing his address as Hayles Buildings in Southwark so we know Ruby and her husband were still in Southwark in 1939.
So the first question is: had Flo and Harry been staying with Ruby when they got married in 1939. The second question is: was Irene Elizabeth actually living with Ruby when she died - in Southwark 1935/SEP. My cousin has vivid memories of Flo and her little shop but has never heard even the slightest whisper of any children and I cannot find any children surname Wrench mmn Kerrison.
The information about Harry Wrench is interesting and I shall encourage my cousin to investigate further as I think he has the makings of a good genealogist and I'm sure he'll find it easier through having your input to help him!!
Thank you again for your help.