After letting the clay dry for a day i decided to start cutting out the eyes using just a normal craft knife and sanding it back using some course wet and dry paper to try getting the basic shape of the helmet.
I then took the helmet off the model head and realised that i had done the eyes the wrong shape so cut them a little more and shaped it again. the eyes were probably the worse part to try and get right and symetrical but in the end i think they look ok.
you could try using a template for the eyes draw them out on a piece of paper, then cut them out, put them on the clay where you want the eyes to be and cut around them with a craft knife. this way you get them lookin symetrical.