I have BT Fibre 1 which says it averages 50 Mbps, since I have bought this I have struggled to even reach 10 Mbps. I have tried everything and nothing has worked. I wanted to talk to BT about this however they removed their online chat support and I do not fancy calling them at this time of the year during lockdown times.
welcome to the BT community forum where customers help customers and only BT employees are the forum mods
in order for the forum members to help please can you post the stats from your router (if hub enter 192.168.1.254 in your browser) and if HH5 then go to troubleshooting then helpdesk and if HH6/SH2 then advanced settings then technical log information .
Have you tried the quiet line test? - dial 17070 option 2 - should hear nothing - best done with a corded phone. if cordless phone you may hear a 'dull hum' which is normal
enter your phone number and post results remember to delete number https://www.broadbandchecker.btwholesale.com/#/ADSL
Someone may then be able to offer help/assistance/suggestions to your problem