Urgh well basically it's all a bit of a mess down there
Hormones were all normal, progesterone was low so basically the 2 days of black clots was my period. Scan showed there didn't seem to be any thickened lining, but there is a visible clot, so he's a bit frustrated as my uterus just doesn't seem to want to give stuff up. Showed me the photos from the hysteroscopy so we could see the bit of tissue that my body just wouldn't expel either.
He thinks the lining I grew this cycle was probably not good quality, as he's concerned about the blood flow if I've only had a clotty bleed. So we're back to needing a good clear out first before we can start a FET
Plan a) is a week of provera and a HyCoSy in 2 weeks time to have a clearer look at the uterine cavity
Plan b) is a month of cyclo-progynova (ie an HRT cycle) where we build fresh lining up with oestrogen and then try to have a withdrawal bleed off that.
Plan c) is another hysteroscopy with a copper coil to treat as if for ashermans, but he's keen to avoid another op.
Said was fine for me to take a daily aspirin, vitamin E, l-arginine etc in the mean time to help with blood flow, said they couldn't hurt. He's just as frustrated as I am, just really hope plan A works.
It's just really sad. The uterine artery blood flow was terrific. The thrombophilia tests showed no evidence of any underlying clotting disorders. But we don't know why I'm just clotting and not having bleeds. He said it might some kind of issue with the vascularisation of the endometrium which maybe compromised the blood flow to the foetus and that's why it died. Basically did my uterus choke the baby to death? 
We just don't know.
On the 'whoa science' front, the PGS report showed no discernible pattern to the aneuploidies (which is good) - a few of them were complex chromosomal abnormalities which he said almost certainly wouldn't have implanted, and a few were trisomies or monosomies which he said would likely have miscarried. The other six were genetically perfect. He said DH and I were obviously 'very compatible' as our eggs and sperm were able to make beautiful embryos.
Which is great. Except that at the moment my uterus is so toxic we can't put anything back. Urgh.