I am 613m from my PCP and my router is synced at around 24Mbps/4Mbps upload. My lowest assured speeds according to the BT retail website is 26Mb and my estimate is around 30-40. I'm on Employee Infinity package and using latest BT Smarthub.
I suspect my line might be alu, which could explain massive drop of speeds, as I am not that far from the PCP to have speeds degraded. And as you can see my capacity is just short off 28Mbps.
4.08 Mbps / 25.04 Mbps
4158 / 27634
6.3 dB / 5.1 dB
are the stats from using the test socket with a filter/ if not can you use test socket to see if that helps
if you have aluminium cable as part of your conenction that would reduce speed and checker estimate would not take that into account
you are only marginally below 26mb connection - what was the minimum guaranteed speed quoted in BT's original letter?
and that is your current speed from your router you can try getting an engineer visit see speed can be improved