Sarah,
I have found a few more dates.
Commissioned as an Acting Pilot Officer / Cadet Pilot on 22 May 1964:
https://www.thegazette.co.uk/London/.../6035/data.pdf
Promoted to Flying Officer on 1 October 1965:
https://www.thegazette.co.uk/London/.../9285/data.pdf
Promoted to Flight Lieutenant on 1 April 1969:
https://www.thegazette.co.uk/London/.../3460/data.pdf