How do I remove the bumper of a Citroen Xsara Picasso? ('02 plate)?

I need to remove the front bumper from my Citroen Xsara Picasso, as I have had a "meeting" with a towbar hitch and need to remove the radiator and fan as they got rather damaged! It is an '02 plate 1.8 petrol if that makes any difference. I have remove the 3 bolts underneath and the 3 star shaped allen key bolts on the top, near the bonnet luck, but it still won't budge. Can anyone help? Or will I need to take it to a garage?