Absolute Zero by Helen Cresswell
When the Bagthorpes discover that Uncle Parker has won a competition prize of a cruise to the Caribbean, they are beside themselves with jealousy. As if he isn't rich enough! Without further ado, the Bagthorpes start entering every competition in sight. But winning ten toasters is not exactly what they had in mind! Only Zero, the family hound, achieves real success - winning a competition all of his own . . . Typical!