Hello and welcome to Rootschat.
Here is the reference for your grandfather's birth.
From
www.freebmd.org.ukMar 1920 Leicester, 7a/358
Benning, Douglas J
Mother's maiden name - Heath
and from there, the marriage reference for his parents.
Dec 1904 Leicester, 7a/417
John Thomas Benning
Elizabeth Heath.
I hope this helps to get you started,
Jen