A non-scheduled Sri Lanka Airlines flight left Dhaka for Melbourne with 220 Australian citizens along with their families early Saturday.    The special flight also carried eight New Zealand citizens and permanent residents on their way back to New Zealand.    Together with 285 passengers who departed from Hazrat Shahjalal International Airport on April 16, over 500 have so far returned home to Australia, said the Australian High Commission in Dhaka.    The High Commission said they, for the second time in three weeks, helped Australian citizens, permanent residents and their immediate families to return to Australia.