She was born in Croydon, South London.
For a number of years she played the part of Frau Schrader (The Baroness) in the London production of The Sound of Music at the Palce Theatre, singing two songs which were cut from the film version.
Gayson was originally to have been a regular in the Bond film series, but her character was dropped. Gayson's voice in Dr. No and From Russia with Love was overdubbed by voice actress Nikki van der Zyl, as were the voices of nearly all the actresses appearing in the first two Bond films, though Gayson's real voice can still be heard in original trailers for Dr. No.
Decades later, Gayson's daughter appeared in a casino scene in the 1995 Bond film GoldenEye.