Ok i have been doing a little digging and i think i can see the problem.

I can see /admin/includes/modules/ but there is no update_product.php file there.

I have looked else where in my directory but cannot see this file anywhere.

Would it be better if i just re installed the application from scratch?

Im not sure how to do it but i can see that there are instructions so should in theory be straight forward.

Would i need to delete the facebook authorization.php file first or any other files before i do a clean install?