sleepy I had a private early scan at 8+3 due to suspecting i was miscarrying and they couldn't see me at EPAU for 4 days! I had another two weeks after for reassurance. I would've had a private one at some point even without the sporting, as I suffer badly with anxiety which has gone through the roof during this pregnancy. It was 100% the right decision for me as its helped ease my mind, I'll still be nervous for my 12 week scan in 10 days but at least I know everything was ok only two weeks beforehand. The risk of miscarriage after seeing a heartbeat at 8 weeks goes down to 2%, then at 10 weeks it's 0.6%. You have to do what's right for you though, most people I know in RL have just happily waited for their 12 week scan.
I'm not doing harmony though although if my downs risk is high, I will be having the amnio. For me at my age (27) I don't see the point of paying hundreds for something which is unusual. I'm still worried about the NT test but will cross that bridge when I get to it. I had literally never heard of harmony until coming on here, one of my friends is 35 and pregnant (so obviously higher risk of downs) and she didn't have harmony, just had the usual NT and bloods.