@cerzi Following up on your idea of finding multiple local cases of the problem, it is not easy. Different ISPs will have different links at the exchange so may not have the problem. Plusnet customers may well have it but they could be from a wide area and not local to you. Smaller exchanges from many miles away use the backhaul network links at larger head end exchanges.
I tried a bit of googling to find out more about these Hot VLANs and found an interesting post in the BT forum.
https://community.bt.com/t5/BT-Fibre-broadband/Superfast-download-speed-lower-than-upload-in-the-eve...
This is quite recent and mentions a lot of engineer visits, some blame being put on the customer for using streaming services! The usual clutching at straws fixes such as a new router and a new card in the FTTC cabinet, then Openreach saying it was not a local issue but some problem further into the network.
Eventually the reason for the problem was found and corrected .... "the VLAN to which I was allocated had been omitted from the automatic load balancing system, which meant that when congestion occurred, the system did not automatically detect and correct it."
I have not come across this automatic load balancing system before, maybe this explains why these peak time speed faults are not common these days. However if you're not included on the system you may well have problems.
Hope this gives you some ammunition to fire at Plusnet if you don't get any progress on fixing the issue.
