I think you might have to bite the bullet, and order
that birth certificate, to get more clues.
Sidney James Keeley ( b. 17 May 1916, according to death entry in Aug 1996 ) mothers maiden name Leek.
can't see any Keeley-Leek marriages, but she could have
been widowed, as this is WW1 era.
I did see a Robert Keeley living with Agnes Lee ( no 'k')
on the 1911 census, near Attleborough, but that's the
closest match I could find.
good luck Phil B