I'vejust solved it!!! Incase anyone else has had this problem of the camera green light coming on and the screen lighting up for a fraction of a second before both go off and the lens fails to pop out:

Look at the camera from the side: If part of the circle that says Pentax lens/3xzoom is at all proud of the outside ring it will prevent the lens from coming out so press it gently down so that it is even all round and VOILA it works! or at least it did for me.