Eddie...its my understanding that Sky still needs a BT landline to work. It may not have a phone attached to it, but its still a physical connection to the house, and only BT can provide it. Whether we call it a telephone line or a landline makes no difference
Virgin uses its own cable network, although that its only available in a small number of locations throughout the UK.
So, for the great majority of people, if you want the internet at home, and you want it to be fast and relatively cheap, a landline is still essential.