Hi Claire, have found that Alice Watson nee Edwards, brother William, with his wife and children, also immigrated 'down under, arriving here on 03 Dec 1841 on the ship 'Columbine'. His immigration records shows both his parents dead so that is maybe why I can't find Edward & Alice on C1841.
Strangely, also with them is William's sister Elizabeth, aged 19 years though she was with Alice on the ship Formosa when it arrived in 1839 ... rather odd?