Unfortunately the closest timetable to 1974 I count find online was April 1971, three years before you flew.
BOAC - British Overseas Airways Corporation
Index of /ttimages/ba2/ba71/
Australian flights are on pages 36 - 43.
I'd like to know if anyone can trace any others.
Its very interesting and well worth a look. A typical flight to SYD would typically have six intermediate stops. I was surprised at home many flights stopped at ZRH, FRA & FCO which, as has been said before, was doubtless a relic of empire days.
You could certainly have flown to SYD with two intermediate stops such as BAH and SIN. You could have reached Perth with one intermediate stop at somewhere such as BOM from 1963 given the range of the 707 320B/C.