You don't need to configure the new router to connect via PPPoA because the connection to the ISP is already being established by the BT Voyager using this protocol. Connect the new router's WAN port by ethernet cable to the the Voyager's LAN port and it will get its IP address by DHCP from the Voyager. Just set it for a "direct connection" or "IP by DHCP", depending on the actual terminology used. It does mean, of course, that the the new router's WAN IP address will actually be an address in one of the ranges reserved for Local Area Networks - a 192.168.x.x or 10.x.x.x subnet. It is important that both routers don't operate and allocate IP addresses in the *same* subnet, i.e. if they both operate in a 192.168.x.x subnet, the third "octet" of the IP addresses must be different for each router.