Ah okay so it shouldn't be too difficult of a fix! Also, the WAN page...is that on the settings page when you log into the router?
Same issue happened to me too. The engineer came, checked and fixed it. The RJ45 was incorrectly plugged in a switch just outside the flat. You'd think they test it when they connect you... They had no idea about the wan page haha, they only cared about the speed test to their data centre.
Have tried connecting straight to the port as well. An engineer is coming to check it all anyways but thought there may be something simple
LAN, via router. But, I noticed that the router was only connecting at 100Mb (easily spotted on the WAN status page) when the service was first enabled. It eventually reconnected at 1Gb. You can try connecting directly to their Ethernet socket instead for testing.
Is that over wifi or ethernet? I'm not getting anywhere close to those speeds on either and I just signed onto the 1Gbps packge.