I have just upgraded to BT Halo 3 Full Fibre 900 and have been expecting download speeds of up to 900mbps as promised by BT. When BT engineer installed it he said everything was fine.
I have not noticed any difference nor improvement in my download speeds and a check (via Wi-Fi) showed a download speed of 41.97mbps and a check plugging my laptop into router via a Ethernet cable (as recommended by BT to give a true download speed) actually shows a speed of 167.4mbps. Of course, the BT Broadband speedchecker was unavailable and could not check.
I would report the line., 167Mbps is well below handback speed anyway. Could have a dirty fibre, or something else.
trivial but couple of things to try:-
1) make sure wirelss is turned off on your pc and try to connect via ethernat again - run test on fast.com
2) try a factory reset (use a pin and press for 2-3 seconds) let it all come round again and re-test