I don't know why my router started working but after I finally got the rubbish HG533 streaming sky. I replaced it with my ASUS RT-AC66U and after some experimentation got it working using the followig seetings. I don't know if the order ofthe setting have any signifcance.
I set the youview box with a fixed IP Address.
Settings/Network& Internet/Wired Connection/ Manual I used 192.168.1.101 subnet Mask 255.255.255.0 router 192.168.1.1
This can aslo be accompished by using the mac address of your youview box and reserving an ip address. use manually assigned around the dhcp list in the LAN settings (DHCP Server)
In the IPTV tab Use DHCP routes RFC3442 & Microsoft.
Enable multicast routing (IGMP Routing)
Enable efficient multicast forwaring (IGMP Snooping
UDP Proxy (Udpxy) 0
In the Wan settings I cloned the MAC address of the HG533 unit. The mac address is written on the outside of the HG533 router. Not sure if this is required but once I had it working didn't want to take this setting off. These settings can be found win the Wan settings Soecial requirements from the ISP. DHCP query frequency set to Normal Mode.
I then used port forwarding to setup a forward from port 1024 to 8081 using the ip address i set up the youview box in this case 192.168.1.101 Again not sure if this really required but...
After this I reset my youview box back to factory settings. Set up the box re-checked the manual IP address again and Sky channels were working.
It will be interesing to see If this carries on working for more that 24 hrs