I have now gone into phpMyadmin and deleted the wp_postmeta database tables as suggested in the thread and the old Attributes have now been deleted from my Locations WP Edit page.
However, is there a way to stop this glitch so duplicate Attributes can be deleted properly in WordPress? I will need to update the Location Attribute names in the future and would prefer not to have to locate my databases each time to delete them!
By the way I am currently using the Twenty Fourteen theme and have no other plugins activated.
