Yes, Guest, the Sydney Opera House is indeed in Sydney (Australia)! This recording of PB and Shirley Collins was made in January 1980 by the Australian Broadcasting Commission as it was known then, and a lot of it was broadcast on the national FM station the following year. A copy of that off-air broadcast, along with the four-part Kipling special Bellamy made for the radio, have been circulating for some years.
If this is the complete concert, then this is gold. Have yet to investigate - an appropriate ANZAC Day task.... It was noted at the time that this was the first "folk" performance at the Sydney Opera House. Some tourist photos of PB outside the venue are included in the booklet to "Wake the Vaulted Echoes," the Free Reed Bellamy anthology.