How much crusherun and crushed granite?

You would need around 6/7 tonne of type 1(stone) for the area your talking about. Seems quite a deep excavation for artifical turf, I'm presuming you have a clay soil? If the drainage is as bad as you say, in affect you will be creating an area full of stone, leaving the water nowhere to go efficiently in heavy or sustained downpours.

You would require 5 ton of type 1 .this is semi permeable though the thicker you go the less drainage this shall have .we would also add drainage holes with shingle and rubble and top with one inch of sand to complete .the sand will give an inch for water to soak into before draining into the ground.