Answer
If you decide that PhormDiscover isn’t for you for any reason, you’ll be able to switch it off at any time for everyone using your broadband connection. Your ISP will record your decision, usually after you’ve demonstrated that you are the account holder. This means that if you choose to opt out, then you and any others users on the connection will have no interaction whatsoever with the PhormDiscover system.
Even if you switch PhormDiscover on at the broadband connection level, others using the internet connection can switch the service off by using their browser settings (either by blocking the Discover.net domain or accepting the PhormDiscover “opted out” cookie).