The Billion 7800 isn't really fast enough to handle 80/40 fibre data.
Billion have said it is but if you look at the support forum it is really pushing it.
The billion has really been used for its ability to get good speeds on long lines with ADSL - this isn't relevant for FTTC. It will only be serving as a router, better devices are available and ISP supplied routers are reasonable.
BT Infinity 2 - IP profile 77 / 20 - super fast!
Previously BE Unlimited - 21,000 Download 1,200 Upload but then moved house - 6,500 Down, 1Mb/s up - gutted!
Ex <n>ildram , been to SKY MAX - 15,225 Download