I don't think these folks will have the same protections as say a census worker. Where I live, all solicitors are required to obtain a permit from townhall. When there's a knock on the door and I recognize them as a solicitor, before they finish their first sentence I ask them if I can see their solictor permit from the townhall. They never have one of course, and when they start making excuses I tell them they should get one or be careful because they might get the police called on them while walking around the neighborhood. Then I close the door.