My personal opinion would be to stick with Sky.
I had NTL Cable TV for 4 years, and I lost count of the times it broke down. Common faults were channels disappearing one day, and returning the next, the picture often stuck (sometimes for hours), and the picture often went pixelated.
I got completely fed up with it all in the end, and about a year ago I had a Sky dish installed.I have not had a problem since.
Also, I believe you can no longer get channel Sky 1 with Virgin.
I still have a Virgin 20MB Broadband (�34.99 pm) and a Virgin landline which I dont use much so it only costs me about �5 a month, and I am really pleased with both of these services.It was just the Virgin TV that drove me mad.