Assuming you want to cruise the whole way, you need a segment of the round the world cruise - try Cunard, Saga and P&O have just announced 2 of their ships doing it on Aurora and Oriana. And there is an old ship called Funchal that regularly plies the waters between here and there,not sure of dates though.
Fred. Olsen's "Black Watch" sails from Southampton on 06 January, 2009 reaching Brisbane on 18 February. It also call at Sydney, Burnie, Melbourne, Adelaide, Burnie and Fremantle.
OK thanks: will check this out.