In the 3rd Party Routers thread I did confirm this router works and confirmed the settings: https://community.bt.com/t5/YouView-Boxes/Multicast-Settings-for-3rd-Party-Routers-may-not-work/m-p/...
I strongly recommend you upgrade the firmware of the router if you haven't done so though.
Most surprised that under LAN/IPTV there's no DHCP option as all the current Asus routers look very much alike in terms of the overall firmware. My RT-N66U had it as does my DSL-AC68U.
I have DCHP server options but I don't specifically have the option to choose the DCHP route (where they say to choose microsoft). I can do screen shots when I get home if that would help?