In a medium-sized bowl, mix together water, olive oil, sugar and yeast. Set aside and let the yeast proof for about 5-10 minutes.
In a large bowl or clean work surface, mix all-purpose flour, semolina flour, and salt together. Make a well in the center.
Gradually pour water/yeast mixture into the well. Using a fork, bring the flour in gradually from the sides and swirl it into the liquid. Keep mixing, when it starts to come together, work the rest of the flour in with your hands. Knead until you have a smooth, springy dough.
Place the ball of dough in a large flour-dusted bowl and flour the top of it. Cover the bowl with a damp cloth and place in a warm place for about an hour until the dough has doubled in size.
Remove the dough to a flour-dusted surface a knead it around to push the air out. You can either use it immediately or keep it, wrapped in plastic wrap in the fridge or freezer until required. Don't roll out the dough until you are ready to cook your pizza.
Divide the dough in 4. Bake according to recipe directions.