SLY didn't allow anybody elses modems to be used until recently, and all they supplied was a locked down combined modem/router with single band wifi. When I read online that the OpenReach modem could connect to SLY, it was off to Ebay. £5 later and I had a modem. Plugged it in in place of the SLY modem, and it connected
The ASUS just plugs into that. The wifi is awesome !!!
As long as you are following instructions that work, you should be fine. You do have to take a leap every now and then though.