I have been looking through the different pages here and thought I should add my account for anyone looking in the future.
I had my 12 week scan yesterday at King's hospital in London. My NT measurement was 3.1. On that basis they rushed my bloods while I waited. So within 2hours I had my risk probabilities. My risk for DS was 1:68 so after taking me through my different options: do nothing, Harmony test, or CVS and taking on board their recommendation, I opted for CVS. They arranged for the procedure to take place immediately.
It was scary but the lack of wait was actually really positive. It wasn't painful but uncomfortable and thankfully over very quickly.
I am now waiting for the preliminary results which should be available within 3 days.