Born to British Mother before 1983

[Lightspeed]

HI,
I want to know what my options are with regards to British Citizenship. I was born in 1970 in South Africa. My Mother is a British Citizen (she was born in Rhodesia which was a Colony at the time) and holds a British Passport. My Grandfather on mother's side was born in the UK. I have the original birth certificates for both of them. Can I apply for British Citizenship and a Passport?

Thank you