TalkTalk don't even both with that you just have to tag your traffic for VLAN 31 and you are good to go.
Can you expand on that?
I've been with Talktalk residential (twice) and never had to VLAN tag any of their traffic.
VLAN 101 on the modem as with all OpenReach FTTC.
The OpenReach ONT adds a similar VLAN tag for FTTP.
You simply need to select DHCP/IPOE on any router and Talktalk automatically assign an IP.
I've never heard of them using VLAN 31 though.