THANK F--K FOR HARMONY everyone!
Today I got my results and I am beyond grateful I got them BEFORE I had my NT screening.. that I did the FMC route with Harmony from the beginning, and not the "NHS - argh crap results - Harmony" route. If it hadn't been for my pregnancy last time screening positive it would never have occurred to me to go for Harmony first.
Harmony is negative 
NT screening is.. a disaster. 1 in 5 risk of T21.
Age: 37
NT: 2.7mm (above 95th percentile)
PAPP-A: 0.73MoM (close to normal)
bHCG: 5.43MoM (WTF is all I can say, it is off most charts)
The bloodwork alone had me at 1 in 16 even before they found the nuchal was high.
I think I would have passed out if I'd got that on the NHS and had to wait two weeks for Harmony.
Nevertheless, having these numbers is useful. The raised nuchal means I have a cardiac scan at 20 weeks as it can indicate issues with the heart that might otherwise be missed on a regular scan. Heart looked fine today but it is too early to be sure.
The high bHCG can indicate an issue with the placenta so I'll need to be regularly checked for growth.
Apparently it also accounts for why I've felt more sick this pregnancy than any of my others. I do have naturally high early betas - this can also make later ones higher. And I had bleeding not long before.. again, that often raises the bHCG. So there are possible benign reasons behind the high level, but still 
I am just beyond grateful that this test exists. My sanity is grateful. My DH is grateful he doesn't have to deal with me flipping out and panicking!
As for the sex, she kindly put it in a sealed envelope that DD1 will open and tell us about later when she gets home from school
I guess they're used to being asked to do this!!