If I plug in the "free" Sky Q Hub I get speeds of around 50 meg, so I think there's something wrong with my HG612. I wanted to continue using it as I use a Cisco router and don't want to double NAT.
Your other option is to buy a new VDSL modem - I suggest Draytek Vigor 130. I use it with Mikrotik hEX PoE and the combination is rock solid.
The Draytek supports "baby jumbo" frames (1508 byte MTU), so you get 1500 byte IP MTU even after PPPoE encapsulation (as long as your router also supports this - the Mikrotik does)
It also has web and telnet interfaces so you can see exactly what speeds the line has synced at. To use this, give your router's WAN port an IP address like 192.168.2.2, in addition to its PPPoE interface. The default IP address of the Vigor is 192.168.2.1. In order to access it from a different subnet you'll either need to set the Vigor's default gateway to 192.168.2.2, or configure your router to NAT all traffic outbound on the 192.168.2.2 interface.
Apart from this, the Vigor needs no configuration, it Just Works™.
And of course it does G.INP and Vectoring - make sure you have the 184.108.40.206_BT firmware.
Edited by candlerb (Sun 25-Feb-18 18:06:04)