Did all of that except contact my ISP. Don't wanna talk to those bitches unless absolutely necessary. As I said, it even affects my phone and tablet so it can't be anything related to my pc, right?
If you are connecting with your phone to the same wifi as your PC, then yes, it seems like it does not relate to a specific computer. Try this: disconnect your router and connect your computer directly to your modem (if your modem has ethernet). If you own an all-in-one modem-router provided by your ISP, it might have went bad.
If the problem persists across not only various browsers but also various devices, you can immediately rule out any problems or solutions directed at a particular browser or device (e.g. a chrome specific fix or flushing your PC’s DNS cache would be irrelevant for you). Instead, your problem can only be something everything shares - your router or your ISP. Completely reset the router. Problem solved? Cool. No? Call your ISP.
It's bloody Cloudflare who's at fault. I thought only Brazilian users were affected but OP is from the UK so I guess it's more widespread.
Taking into account that two of you in the same country have the same issue, and that a VPN resolves it, it's probably either the ISP or Cloudflare not playing nice with the ISP. Maybe getting a new IP helps. Tried ipconfig /renew? Or turning the router off and on again? Edit: nevermind, it's UK and Brazil. Cloudflare maybe? But I guess there's something going on then, for CF to spazz out like that.