I am helping someone who is new to this!
She is looking for information on her birth father and his family.
Olive was born in Strood in 1924?
I did find her birth in 1962 Hackney London mother Olive and father Frank Grant!
I couldn’t find a marriage so like you think they were not married.
Have you tried 1939 register?
Thomas Pack and wife Annie,
2 records officially closed and
three children named, born 1928, 1931 & 1933
Was his occupation listed on the 1962 birth certificate?
Did her mother marry?
Perhaps her father was a similar age

I'm sending you a PM with some information so you can take a look and see whether you think it's relevant to your F W Grant.