Thanks for the responses.
I tried setting up using a laptop connected to the net via WiFi and using Ethernet from laptop to sky box but the sky box can only connect to the local network and will not access the net. I also tried the same setup but also creating a network bridge between WiFi and Ethernet in adaptor settings in Win 7. I will try this approach again later.
I have 3 spare dir615 routers so will try to update the firmware to ddwrt and setup a WiFi bridge as an alternative.
My dir615 routers have H/W Ver D4 with 1.00VG firmware. Can I update from this version?