Just to clear things up infinity doesnt use vdsl it uses PPPoE
Just to clear that up Fibre over Copper uses either a VDSL modem or combined VDSL/Router PPPoE is the communication part without the Modem there is no PPPoE.
BT phased out there separate VDSL modem and separate HH3 router for the combination HH5 with both built in.
So presently the OP cannot use a 3rd party router without it having a VDSL modem built into it, He could of course seek out a secondhand official VDSL Modem from Ebay but for this you have to determine which cabinet you are connected to as BT use 2 types of VDSL modems for 2 different CABS.
You are either connected to a Huawei or ECi Cabinet so you have to identify which one your connected to before you purchase a separate modem as they are not interchangeable and only work with the correct one.
Best of Luck
