Ah thanks and makes sense. No im currently using skys own router (as modem only) and my router for all the networking. dhcp, LAN and Wifi etc.
None of the Sky Hubs support bridge mode (modem mode).
Bridge mode is where the modem syncs with the network operators kit at the other end of your local loop, and nothing else.
What you're currently doing is syncing with the sky Hub, and also doing the authenticating with the Sky hub (getting your WAN IP).
Your router is doing everything else but the authentication.
When you switch to FTTP the Sky Hub will be swapped with an ONT.
The ONT won't do the authentication with your ISP. You'll need to add that part to your router.