I have just had full fibre installed about two weeks ago and I am only getting between 30mb and 60 mbps. I have had an engineer out who tell me that I am getting 926mbps in the house but cannot understand why it ends up so slow.
The engineer changed the smart hub 2 , and it was exactly the same, he then changed all the leads and the white Modem box and still nothing has helped.
I do not know much about these things but it is driving me daft wondering if I should return to my old Smart Hub and forget the Smart hub 2 and see if that helps.
If your old smart hub has an ethernet WAN port give it a go.