BT changed me over from ADSL to VDSL this week.
I made at the appropriate changes in the network configuration , PPPoE, dsl0.101 etc etc.
I could not get it to work, kept getting NEGOTIATIONS_FAILURE message in the wan setup .
The physical VDSL settings seem ok, seeing a connection being made under the status window, but was not receiving any IP address sett for WAN connection.
After a lot of hair pulling and trail and error, I got it to work by adding a dummy password in the chaps credential settings. Looks like an empty password string does not work for BT in our exchange ( Ford in Scotland)
So if you can't get it to work, try adding a password to the setup under
config interface 'wan' option proto 'pppoe' option username 'firstname.lastname@example.org' option ipv6 '0' option ifname 'dsl0.101' option password 'test'