Thank you for your answer Nic
Thanks to your help I have worked out how I can now unlock them from the edit in the gradebook.
However there isn't any reason I can come up with that they should have become locked in the first place. I have only ever marked from the Assignment Module. (I used the Gradebook illustration in my post as I thought that it showed the problem better)
so if you (or anyone) does know how this might have happened or how I can globally un-override I would be very grateful as there are alot that need to be selected and unoverriden or underridden what ever the opposite is.