I used an alternative router ages ago, to be able to have Wireless "N" back when Sky's router was still ye olde Netgear DG834GT. This was back before the change from PPPoA to MER though (are you definitely still using PPPoA?). I just put my ADSL connection info into the non-Sky router and away I went...
Tbh, you may be better off asking somewhere dedicated to Sky. You could try the
forums at Sky User.