Thanks everyone. I've played another 20 or so games applying your tips and I fin sky feel I have an element of control when I don't have the ball.
I was having the same problems. Got the game yesterday and haven't played since FIFA10. But then I found an option to change the defending back to the old school defending. Guess they didn't have that in 12. But as you seem to be improving with the new style defending I don't suppose there is any point in changing it now. Maybe I should change it back and use some of the tips on here to learn how to use it,