Can only give general advice but look in current router for its ADSL settings, incl.
Encapsulation VC MUX/LLC
Internet IP Address Dynamic/Static
DNS IP Address Obtain from ISP/Manual
Connection Type Always Connected/Auto - Trigger by Traffic
Swap routers, without connecting to filter. Put the values you found in similar fields of the ADSL settings of new router.
Connect to filter and hope
If using wireless, you may have to do similar with wireless settings.
1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 19 Meg WBC