Kings are world leaders in nuchal scanning (was developed there) and so I personally would not waste the money at Harley St, it won't change the results. Getting the results from the CVS is the most important priority and will probably need chasing (I would even get your midwife to chase a bit early to try and cut down the wait). Try and have your partner with you when you chase so that you are both together when you get them. Everyone I know who had increased risk (remember that that is what it is (even a 1/4 chance means 75% of being ok) including myself, went on to have a healthy baby so it is not unlikely (but obviously people discuss 'negative' outcomes less). By being at kings they will also check really carefully if downs is ruled out, for heart defects, and again it is incredible what they can check with their specialism (couldn't believe the detail of the unobtrusive heart scan). You are so lucky to be at Kings for this, you really are in the best place. I hope things work out ok for you.