I think there's another element driving VS. As long as they have to put their passengers on BA domestics there is a commercial issue. BA will lift the ticket coupon at Manchester and that will give them visibility of the fare ladder routing etc. With their own flights they can keep that data in house. It also extends their reach for Upper Class because they will be able to offer limo service to a large tranche of the NW plus most of the populated bits of Scotland (even Glasgow).