When you have Sky, you have to deal with Setanta separately, the benefit of virgin cable now is that it is all done through them and you don't have to deal with Setanta at all.
When I was on Sky in 07 and cancelled Setanta I had the same problems as everyone else, i.e. zillions of phone calls for ages, even though I told them I was going to china!!
In the end, as soon as I answered the phone and they mentioned Setanta, I went on the offensive and politely asked for their personal details, full name, personal phone number etc etc so that "I could get the exact details correct when I take the company to court for harrassment".
The calls stopped soon after!
Half the problem is that it's not the fault of the people phoning, I'm guessing they just come to work and get given a list of names and numbers to try and persuade people not to cancel, they probably don't know that they are the tenth person to make the same call!