Number3 Well, I had my booking on 4th December and MW said she would make the appointment next day. Two weeks later still had not heard so rang MW who called them and then called me back to say scan was on 8th January. Still no letter arrived. Eventually I rang hospital on Monday to double check, and lady said she would send out another letter. Still no letter and I've had the scan now!
I really don't think they had a good reason not to fit me in at a sensible date so I could have a chance for the nuchal. MW knew my cycle and we booked ages in advance. Even Christmas does not seem like a good reason really. And there is something really wrong with their booking system! Not impressed. 
Fortunately, my head is full of lovely memories of tiny brain, tiny lungs, tiny beating heart, tiny spine, little legs, arms... etc. etc. etc. so far too happy to care right now about having blood test in 2 weeks instead. 