Hi Alan I do think you maybe correct re William James as his father David James remarried a Martha Garrett and came to Aust in 1881 & he is not on the passenger list

Martha,Beatrice,Emily,Annie,Rose,David arrived on "Merkara"as remittance passengers. David arrived earlier. The Merkara inaugurated a new regular mail service on 12th Feb 1881 when she left London for Naples,Suez,Colombo,Batavia,Cooktown,Townsville,Rockhamton

David & Martha and 3 children David 10, Francis 7,& Mabel 6 returned to Wales/England on the "Orotava" 7 Nov 1894 but cannot find Annie or a m/d for her

I know her sisters Beatrice & Emily m & stayed in Aust