We finally have confirmation that the FireBrick FB2700 works with BT FTTC lines and can provide full 1500 byte MTU IPv4 and IPv6 native using PPPoE to the BT VDSL modem.
Well done team.
(yes, that is 3 of us working on this on new year's day at 10pm, we are totally mad)
We'll release new code tomorrow which makes this all automatic when an FTTC or FTTP line is detected, so making the config really simple.
[yes, going for most relevant acronyms in a blog post title of 2011 award]