I think you might have not turned "Picture Overscan" on the tv to ON which might cure your problem. What you need to do is press MENU on the tv remote, then go to SETUP then to OTHER SETTINGS, while your in there go to PICTURE OVERSCAN and change from OFF to ON. What you should notice is that the picture will slightly expand to fit the screen.
If it's the Sky+ HD box that causes these bands only, then simply on the remote press TV GUIDE, then press up to access the main option bar and move along to SETUP then go to PICTURE and make sure the RF1 and RF2 picture format are both set to 16:9.
I hope this works for you.