Fantome
Sepal was an Australian company which was later acquired by Adastra. Suspect you might mean Selco. Is this the aeroplane in question?
VH-UMS
Adastra had their own Catalina:
VH-AGB
There was another survey Cat operated by Geoterrex. This is the aircraft now at the RAAF Museum:
VH-EXG
Alighting on Rose Bay was a brave call. The survey gear was probably worth more than the aeroplane!
Rgds