Since it fails to come up automatically anymore, probably too soon, trying another way.
http://www.vanbommelonline.nl/2011/10/setup-ipv6-using-aiccu-in-debian.html
Disable the autostart.
Edit /etc/network/interfaces
auto sixxs
iface sixxs inet6 manual
up ip link set mtu 1480 dev $IFACE
pre-up invoke-rc.d aiccu start
post-down invoke-rc.d aiccu stop
Next step: get a valid IPv6 dns added on start.
All irrelevant - sixxs shut down - for the same reason that BT Ignite did. It's all worked out now. Also SIXXS noticed take up was slowed and maybe they were preventing ISPs getting complained at.
