Are PressTV and RT banned? Is there a list of banned sites and tech used?

I can't seem to access https://www.presstv.ir or https://www.rt.com

Are these banned in the UK?

Is there a list of sites banned in the UK (whether by ofcom or any other agency or company)?

I couldn't find any news stories or discussions about this. How does the UK banning people from being able to access foreign news sites apparently just fly under the radar?

What is the technology used?

Thanks.