If you're talking the DH.106 Comet, it was never on the Australian aircraft register. Qantas took options but they were subsequently cancelled after the Comet 1 catastrophic failures. Only 114 Comets of all varients were built.
If you're talking the DH.88 Comet, I seriously doubt any were ever operated in Australia except during the 1934 MacRobertson Air Race. Only five were ever built.