if it was the openreach modem that no longer works then you need the router set up on modem/router mode and the rj11 cable connected from wall socket to dsl connection on hub
Username is firstname.lastname@example.org and password BT (if router insists on one). Is there an option to set VLAN, if so set it to 101.
did this guide come with router http://support.billion.com/_Internet/qsg/BiPAC-8800NL-QSGEN.pdf
I'm afraid I'm out of ideas then. You could try setting it up in bridge mode and let the hub deal with the PPP session and see if that works.