I have the same problem. I'm on the Zen Fibre (FTTC) product and my OpenReach modem is lit up as normal and has been rebooted, and my Apple Airport Express which is connected to it using PPPoE is working normally but is no longer getting one of my static addresses but instead is getting a 172.x.y.z. address and is not routing to the internet.
Zen have reported the outage here: http://status.zensupport.co.uk/active/5/3505
Currently tethered to my iPhone.
ZeN Zen Active up to 20Mbps
Speedtouch 516v6 Router
Apple Time Capsule