We've been having issues with our speed bottoming out at irregular intervals - it only seems to happen in the evenings but is intermittent. It's become impossible to stream video.
I ran the speed tests - with a wired connection to the router it doesn't seem so bad, but the Wi-Fi speed is terrible, even standing in the vicinity of the router (last image). When changing the settings in the router at one point it refused to connect and said "You may be subject to a BT network outage. Wait 10 minutes and then press the Connect button.", but was fine a minute later. There are no reported faults appearing in our area on their service status.