Who was the informant of William's death in 1968?
Have you searched the probate registry in case he left a will?
I haven't bought his death certificate but bought his burial from Deceased Online which wasn't very helpful. I'm not able to purchase wills or certificates at the moment.
In case William Timothy was in a de facto relationship with Kathleen, I had a look for Saunders births with mother's maiden name Saunders in Greenwich. They are too recent to post on here, but there is a birth registered there in 1952 with a first name and initial which may suggest a possible connection within this family. (There are later possibilities too).
That's amazing. Thank you for finding that and for teaching me something new. I'm not sure about the other births but your 1952 birth looks quite promising. William was born in 1905, only about 20 years older than Kathleen which I don't think would've been too uncommon.
Kathleen and William are my Grandparents. Kathleen died in 2001. They had 4 Children.