I've just moved ove to fibre large and I'm getting near the top end of sync speeds which is great :-)
I'm currently on wifi connected to my 5Ghz SSID and getting about 70Mb down and 18up but if I switch to 2.4Ghz it struggles to even complete a speedtest and if it does it will hit no more than 20Mb. It times out mostly
Given I'm in the next room and the 5Ghz signal isn't as strong over distances, this seems strange, Could there be something up with the router? (HG633)
Just to help with diagnosis, the firmware is 1.18t