The posts you made earlier when you said you were having issues were all from an ipv6 address with BT. The post you just made now is from an ipv4 address with BT. All the other posts from people having issues were also from ipv6 addresses with BT, so they probably had an issue on their ipv6 network.
Don’t know if it helps, but I believe one way to tell you are having problems is you can access sites like google / YouTube ok but not other sites. Daughters laptop kept doing it, turned IPV6 off and been ok since.
windows 10 ? right click network and go to network settings. Then adapter settings, depending on whether it’s wifi or Ethernet. Right click and select properties - in there can turn IPV6 off.
Not sure if you can turn it off on an iPad or iPhone. could probably turn it off at the router if you are feeling brave.
Mines just got quicker than a quick thing on a very fast thing. Edit gone back to laggy than a laggy thing sat on something very laggy