Hi
Re the possible Chamberlain marriage for Hannah. It was just looking through the possibilities on FreeBMD, there aren't that many likely ones. As you say, Hannah doesn't seem to be around as Stephens in 1939.
Of course I don't know for sure it is right, but, yes, the probate record looks promising.
If Hannah did marry Arthur Gordon, then the 1942 probate record for him gives an address of 6 Grange Road Ellacombe Torquay.
Now I don't have access to much at home nowadays, but the free index to the 1939 Register has
Hannah Chamberlain, born 1912, living at 6 Grange Road, Torquay M.B., Devon. She seems to be married but on her own on the night.
Date of birth seems to be 11 August. Obviously 1912 is well out from 1908, but perhaps if her husband was younger than her, Hannah wasn't entirely up front about her year of birth.
When you get the birth certificate of Sarah / Hannah it will be interesting to see if she was born on 11 August!
There is a Hannah Chamberlain indexed on the London electoral registers in Hayes & Harlington (well two Hannahs actually, but one of them has other forenames/initials)
But I don't know if that might be her, as I can't see where exactly she is living, and whether anyone else is at the address.
As to Hilda, it all sounds very mysterious. Is there anything else you know about her?
John