Thanks for your replies kosher baker, gina and deejay debi.
I am using a recipe from the cheesemaking book by paul peacock,
I have been using 100 litres of milk, (it pains me to say, what a waste!)
warming the milk to 40 degrees C, adding the rennet (3 dessert spoons) cutting into 0.5 cm cubes and heating to 52 C over an hour.
I pressed the cheese for 12 hours the first time, the second time I tried 2 days but there was no difference in the texture. Am I using too much rennet perhaps ?
I used 69 lb (UK) in weights.
I will also look through the parmesan threads when I have time !
Thanks