> 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

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.