How long was it between ordering to having a service? We have three months left on our virgin contract, and are also KCI2, would quite like to time it to have fttp install as near as possible till we are out of contract with virgin.
I suggest you order it now.
There is a risk of paying for some overlap, at worst nearly three months. But personally, I'd rather that than either the risk of paying huge out-of-contract rates for Virgin, or the risk of being left without broadband at all.
Also, there are plenty of "Black Friday" deals on at the moment which should make the overlap less painful.