I've recently swapped my 100Mbps to 350Mbps. The engineer came earlier today but I've been checking speeds and only get 85Mbps wired with a CAT6 directly to the Hub3. I've checked my network status in the broadband configuration and it states:
Primary Downstream Service Flow
Primary Upstream Service Flow
The max traffic rate looks fine, and since you're using CAT6 it feels unlikely that it's a cable issue.. are you certain the network card is a 1gb NIC?
Either check "connected devices" on the hub, and see what it reports as the link speed, or check the link speed on the device you're connected with..