I'm not going to be baited into debating it here, because that will just de-rail the thread. So I'm going to correct the misinformation and then shut up.
Your claim that there is general Internet filtering in the UK in the sense that any reasonable person would understand by that phrase doesn't hold water. China, yes, Turkey yes, Egypt, yes, UK no. I have never, ever, in all my years using the Internet from the UK (1993-present) encountered a page saying "You're not allowed to see that". Then again, I've never gone looking for child pornography which is the only thing (other than the aforementioned court ordered blocks) that is ever officially filtered, and that is not by all ISPs by any means.
That some ISPs, mostly mobile phone providers, provide opt-in or opt-out content filtering is not a UK phenomenon, ISPs the world over offer some variety of 'family-friendly' Internet. This is not the same as your implication that 'the UK filters the Internet'.
The reason that I have a fair insight into how the UK Internet really works is because I was the network manager for one of the UK's earliest ISPs (10th to start by my count), was there the day that the LINX voted to fund the Internet Watch Foundation (who provide the filter lists for child pornography sites), was a non-executive director of the London Internet Exchange for years, stayed in the business until the mid 2000s and still have plenty of contact with people who are still at the coal face. If there were sub-rosa activity to filter content that the general public didn't know about, I probably would.
The putative "porn blocking" doesn't actually exist yet, is not actually blocking, and at the rate it is going it probably never will. It was a sop to certain pressure groups (i.e. the DUP) and they are just discovering that saying "let there be age verification" and actually doing it are two very, very different things. Anyway, the onus on age-verification is on the porn sites, they're not being filtered. It's just the same as bars, prove your age or we won't let you in to partake. Sure, blocking for non-compliance is a possibility, but so is having your bar shut down if you regularly serve under-age drinkers.
Let's be clear that you are actively debating it here. That ship has sailed and backing out later under the guise of this proclamation isn't going to save face.
You should also be careful not to shoot the messenger. The reasonable person you speak of would understand that a well respected journalist organisation, from a sector with a large stake in and knowledge of freedom of information, has listed the UK as an enemy of the internet. So Iran yes. China yes. UK yes. It is what it is. As you could read in the article I linked the blocking started in the mid 2000's and escalated from there, so it's very possible you missed it.
It's also important to note that it's not just about heinous crimes committed against children. Few people will object to that and that type of content was actually the first to be blocked. Overblocking has occurred in many categories, amongst which political satire, feminism and gay content, civil liberties and computing sites, but also Childline, NSPCC, and Police websites.
https://en.wikipedia.org/wiki/Internet_censorship_in_the_United_Kingdomhttps://www.independent.co.uk/life-style/gadgets-and-tech/uk-branded-an-enemy-of-the-internet-for-the-first-time-by-reporters-without-borders-9196571.html"Since the mid-2000s there has been a gradual shift toward increased surveillance and police measures in the UK. National security concerns, the need to fight terrorism and crime, and issues regarding child protection have resulted in the state introducing extensive surveillance measures over online communications as well as filtering and tracking practices. In some cases these are encouraged or required by the state and used by state agencies. In others they are voluntarily implemented by private operators (e.g., internet service providers).[5]
The country was listed among the "Enemies of the Internet" in 2014 by Reporters Without Borders,[6] a category of countries with the highest level of internet censorship and surveillance that "mark themselves out not just for their capacity to censor news and information online but also for their almost systematic repression of Internet users".[7] Other major economies listed in this category include China, Iran, Pakistan, Russia and Saudi Arabia.
Current situation
Internet customers in the UK are prohibited from accessing a range of web sites by default, because they have their Internet access filtered by their ISPs. The filtering program has applied to new ISP customers since the end of 2013, and has been extended to existing users on a rolling basis. A voluntary code of practice agreed by all four major ISPs[8] means that customers have to 'opt out' of the ISP filtering to gain access to the blocked content.[9] However, the complex nature of the active monitoring systems means that users cannot usually opt out of the monitoring and re-routing of their data traffic, something which may render their data security vulnerable. The range of content blocked by ISPs can be varied over time.[10] Categories blocked across the major ISPs include: Dating, Drugs, Alcohol and Tobacco, File sharing, Gambling, Games, Pornography, Nudity, Social networking, Suicide and Self-harm, Weapons and violence, Obscenity, Criminal Skills, Hate, Media Streaming, Fashion and Beauty, Gore, Cyberbullying, Hacking and Web-blocking circumvention tools"