There is 2 problems I see one of which is mentioned on link. What if the requested resource is subject to non disclosure that it was blocked? The other is the

There is 2 problems I see one of which is mentioned on link. What if the requested resource is subject to non disclosure that it was blocked? The other is the increasing use of HTTPS, when a U.K. ISP blocks a site that's using https it just breaks the connection and you get a SSL error and not a http error code. If they served up a page the cert would be invalid unless they were able to supply a cert for the common name you requested.