The UK ISPs already did this earlier. What Ofcom really wanted is to flex their muscle and kill 4chan because it represents Satan for them.
What Ofcom wants next is to make VPNs illegal.
4chan and Kiwi Farms, which is something the article intentionally glosses over. Honestly, KF is a far more “dangerous” place in the eyes of the UK government, as 4chan hasn’t been relevant for around a decade, and the combined efforts to deplatform KF traditionally has been fruitless.
Did they fully block it or just put it on the blocklists that you can turn off in your account settings?
https://www.blocked.org.uk/site/http://www.4chan.org suggests the latter to me, but the checks aren't very recent