Your issue might be that your dish is not properly aligned. I had this issue when the new HD channels came on. They came out did a realignment and all is fine now.
Trust me these lines have nothing to do with the BBC's. They were there last week also at the end of Nip-n-Tuck. Only when they show the coming attractions when there is no HD feed from FX.
I got mine two nights ago. I got all the channels when I got home yesterday with no problems at 6 PM. I would think as you acess the channels your internet connectiion is downloading the channel info / programs and such.