Dissolve yeast and sugar in a cup of warm water. Let stand 5 to 6 minutes, until mixture is foamy.
In a large bowl, mix together half the flour, remaining water and melted margarine. Add yeast mixture, and stir to combine.
Work in remaining flour a bit at a time until a soft dough forms.
Transfer dough to a lightly floured surface, and knead for 10 minutes.
Put dough in large plastic bag, and place in refrigerator. Let rise until tripled in size for about 2 hours.
Grease a round pan, and sprinkle lightly with flour. Roll out the dough to fit the pan, stretching it to fit.
Brush crust with cooking oil, and add the toppings starting by spreading a layer of bbq sauce for the bbq chicken and mushroom pizza and ending with the grated cheese.
Bake at 240°C/220°C for 15 to 20 minutes or until base is crisp and cheese melted.