how much will I use per square meter of hardcore at 75mm deep

The answer to your question is 10 x 10 x 075mm deep is 15 tons Peter

Hello, If you are putting in a base for a driveway, unless you are building off bedrock I would advise you use Type 1 MOT crushed quarry stone to a minimum depth of 150mm. There are a lot of free sites on the internet that will calculate the amount of material required but if you have a 10m x 10m x 150mm space then you'll need 15 cubic meters. I suggest you buy direct from the quarry and save yourself a small fortune. Good luck Andrew May