I have fixed this by renaming the boolean fields to "authenticate_projects", "authenticate_project_action_plans" etc etc.
Now they are working as boolean fields and I can check them etc.
It seems that they activerecord association was somehow being applied to the field in the simple_form active_admin view so must have been trying to return the users projects or users project action plans so I would have a collection being input and so it would try and default it to the select box. Obviously without specifying which field from the collection to use as the value it was giving the dreaded # or whatever it is. And not 'dreaded' but I seem to hit this wall a lot so it dreads me.