Your deffo' doing all the right things Kathryn,
maybe when you ring the library try and find out what records they do hold,
as MIGHt be worth a visit in the future if all else fails, write down what you
think you might want to see and ask if they hold such things.
SOMEWHERE there will be other members of family maybe just vaguely interested at the
moment, could be someone connected to Edith's family that could explain the mysteries to you,
the death records with or without a subscription is not really going to help, especially as you
don't know a birth etc for her.
If George did have another family then hopefully they will be out there looking or interested,
i see your also on on Genes, so again all options being covered, one day one of those obscure hot matches
may throw up an answer, HOPEFULLY someone will be in the same boat as you, ie they know all about Edith
but nothing re George, even the electoral rolls if they lived on their own will only give you what you have now.
Did George leave a will, maybe you could look for one, IF you can find his grave then hopefully then who paid for it etc
might follow, also check the local paper for the funeral as in 60's 70's etc etc they tended to list who was at the funeral.
Maybe write or email a letter in a couple of the local papers, and hope that some relatives are still there,
even this post will hopefully show up in search engines, so anyone not sure where to start will be led here
IF he did die and was buried in Streatham Cemetery, then if it is the same area i am thinking about,
it is next door to the Jewish Cemetery and i visited there on a trip to London, and Streatham Cemetery has its own office at the Cemetery, maybe try ringing them? 020 86794164.