Do you want the Sky phone? If not, don't use it. You can get a stand alone VOIP adapter that plugs into any router you choose, Then select any VOIP phone line supplier that you wish........
Sky supplied me with another ADSL/VDSL router when I got my latest deal with them. I have used it, but I am using it as little more than a modem. I have set up a static route on the sky modem, which is also the nominated DMZ address, so that all incoming traffic is diverted off to my Netgear cable type router. The Netgear router allows me to set up it's WiFi, my nominated DNS for all my network's users. The Netgear router also has 2 different Grandstream ATAs for my 2 Sipgate VOIP phone lines.