Am in the CT9 area if that helps at all, I've been experiencing this for quite some time: upload speeds are around the same or slightly better than the guaranteed minimum of 18Mbps, while download speeds are averaging around 37-39Mbps, despite the fact that the guaranteed minimum is apparently 49Mbps.
No engineers have been seen as of yet about this, I should mention I'm not the one paying for the broadband though I live in the same house and have tried to fix things.
We're using a Home Hub 5 which was installed around July 2015-ish over IPv4 only (apparently IPv6 isn't supported), subnet mask and internal router IP hasn't been touched. Initially when we first got it we were averaging around 50-60Mbps but 2 years later (from about the end of 2016 onwards) it started falling gradually and becoming a lot more inconsistent.
I tried using the default DNS, Google DNS and CloudFlare DNS on a few different devices to no drastic effect or change.
Nothing's running outbound except a TCP port currently not assigned to any device for now. Not running a VPN or some other thing that could be slowing it...
I also rebooted the router 20 minutes ago to no effect... am at a loss here...
post stats from hh5 troubleshooting then helpdesk
enter phone number and post results remember delete number but leave exchange and cab https://www.dslchecker.bt.com/adsl/adslchecker.welcome
try quiet line test dial 17070 option 2 should be silent and best with corded phone from test socket
the speeds quoted by BT are connection speeds not download speed - no ISP guarantees download/upload speeds
dslchecker shows estimated connection speeed range 80/68mb
can you post router stats post here rather than link as saves jumping between pages
quiet line test?