Dear Google: remember that "don't be evil" thing? This is evil.
What is it about extreme internet content that you think is so important that BT should support it being downloaded via their customers home routers without those customers knowledge? Or is it that schools use such a system to block extreme content - presumably you think that the dreggs of the internet are appropriate for schools to allow students to access easily?
Google's not stopping you searching for whatever extreme content you like they're just limiting their enablement of such searches in circumstances where those in control of the internet connection choose for it to be limited.
2. They're invading the privacy of everyone not downloading 'extreme content'.
3. Privacy invasion is not appropriate in anything that pretends to be generic internet access, extreme or not.
Their routers seem to have no QOS - one computer doing an update will kill internet for others in the house, presumable this is the same if other users are on the 'BT Openworld' wifi it shares.
Especially when changing the CNAME record is something that absolutely any DNS provider could be doing anyway...