I found that connection speeds were almost identical to my Billion 7800n (configured for 6dB margin), but...

My PC didn't see the router over Ethernet unless I manually downgraded the config from gigabit to 10/100. The LED on the back of the router didn't even light up.

The router itself is only 10/100, but it should force an automatic downgrade without having to be manually configured.

Given I run the Billion over a 10m extension from the master socket, I'm considering re-configuring the TG582n as modem-only, then connecting that over ethernet to the EWAN socket on the Billion.

cheers, Martin