Sky1 SD should be on the Mix package, but not the HD version as per the latest ChannelGuide
Are you missing any other channels?
Using your remote control go to
Help & Settings > Help > Virgin TV > go up to the top of the screen then TV Care and press OK > Missing Channels.? > Refresh my channels list
Dave
The Service you do for others is the rent you pay for your room here on Earth - Muhammad Ali