https://news.ycombinator.com/item?id=45430848 is the thread where I learned of this. I'll have to do more research, thanks.
https://www.privateinternetaccess.com/blog/internet-archive-...
https://www.privateinternetaccess.com/blog/internet-archive-...
archive.org is blocked (along with other nsfw type sites), but as the last post in your link to an earlier discussion says, I could get it unblocked by filling in a declaration that I'm over 18. Paying by credit card isn't enough to unblock automatically for this particular package.
I've chosen not to unblock for no particular reason. The block sort of makes sense to me because archive.org records a lot of Web sites, some of which may have what is regarded as adult content, and it is unreasonable to expect archive.org to label individual records of sites according to the criteria the UK uses (each country probably has its own set of criteria e.g. gambling Web sites of certain kinds in the US).
archive.org is easily accessible in the UK from most wifi connections in cafes, libraries and, hilariously, colleges (where people under 18 gather in large numbers), and also from domestic adsl or fibre Internet connections.
That's something to do with your provider. Maybe you need a non-crappy provider.
You do not need to provide any kind of declaration that you're over 18 to access archive.org in the UK.
Given that you can buy a SIM that'll give you a couple of hundred GB of data for under a tenner, it seems reasonable that they'd block stuff you didn't want young children getting access to (easily).
Source: am British, on phone.