Make sure it is Virgin you chase up, don't speak to Sky on it.
Having received the email from Sky clearly Virgin have initiated the One Touch Switch process, for whatever reason it hasn't been concluded. The reason I say don't speak to Sky is that it is for Virgin to deal with the whole process, You don't want to lose the benefits of talking to just the new provider, and in particular the advantage you don't have to pay for any notice period with One Touch Switch, which you would potentially have to do if you cancelled Sky yourself.
If you are currently paying for both, I would initiate a complaint with Virgin, they should compensate you. If the complaint gets deadlocked then take it as far as the Ombudsman, it is an Ofcom regulated procedure. That is independent of the cause - even if it is at Sky's end it is still for Virgin Media to deal with, you don't.