OP- have you been offered a 2nd scanning to check the NT? Seems odd that they only try once, and if not visible, that's it! I'd ask again.
I had NIPT and SO glad we did. 1st pregnancy age 38. I had it at 10 weeks- the earliest it can be done, and results showed patau syndrome (trisomy 13). The private clinic booked me for a detailed scan which showed NT 6.5mm, cleft face (not just cleft lip!) and several other abnormalities that were even obvious to me on the screen! I was give the option of CVS or amnio, but due to the obvious issues, we chose TFMR.
Its a personal thing, and something you need to discuss with OH before having the NIPT. It was still a shock to have that diagnosis, but I had to keep thinking of the positives- as odd as that sounds. Being able to chose the TFRM, was one of the few things that I could control. I knew I was having it done very early on, and I wouldn't suddenly MC whilst at work, or go to term and have a still born, or bring the slim chance of giving birth to a baby that was alive, but going to die in pain within hours. Having the choice so early, meant we could mourn, and get back to TTC as soon as ready.
I then had a MC, and currently 7 weeks with 3rd pregnancy. We plan to have the NIPT again, and currently looking at another version called panorama. It can apparently be done from 9 weeks. In addition to the tests that NIPT cover it also includes angelman syndrome, prader-willi and other depletion conditions. I only heard of it yesterday, so I'm still researching whether its worth it, as about £100 extra.
1 thing to consider, is that some clinics still send the blood samples to labs in USA. The turn around time for this is obviously longer, and there is a small risk of them going missing or taking even longer with the current crisis. More and more labs are processing them now in the UK, so those are the only ones we are considering. Look around, because many private clinics will include additional scans, which you may/may not get benefit from. best of luck x