I didn’t know whether the valuer was on the doorstep, in his car, in a cafe, gone off to another appointment in the meantime, gone to answer emails. I had no communication with him.
Come off it surely you can see you are being a bit unreasonable with this "I didn't know where he was" line you keep saying. Surely the decent human reaction is to assume that he is standing on the doorstep or hovering somewhere nearby waiting for you to let him in. If you weren't sure, the normal decent human thing to do is to go to the door, go outside and make it very obvious you're looking up and down the street for him, so that if he's waiting in a car he will see you and make himself known. That way you could have talked to him directly.
You said in other posts that you didn't know he was there. But you did, and he knows you did because your DP communicated that to him. I think he would have been rude if he'd have knocked after that, it makes him look impatient and inconsiderate towards a new mother and newborn. He knew you knew he was there and that he was waiting. He was relying on normal sensible human code of conduct that you'd answer the door after that.
I think it would have been a lot more sensible and logical to answer the door after having got yourself decent (not make up and polished, just perhaps wearing more than a nightie), and half-apologised, half explained to him that you aren't ready because you were expecting them at 1pm.
I'm going to assume a healthy dollop of sleep deprivation, hormones and being in recovery from birth might be clouding your judgement on this. That's perfectly OK, normal, to be expected, and you shouldn't be being judged for it.
Your DH was being unreasonable to have not realised until this morning that the appointment actually made was 8am. He was unreasonable to have expected a mother who has recently given birth and who is caring for a newborn to tidy a house in a few minutes. You were not unreasonable to have thought you had several hours to tidy the house in the morning before a 1pm appointment.
Do I think you both should be cut a bit of slack and chalk the thing up to unfortunate circumstances? Yes absolutely.
The agent is perfectly reasonable.
The person who booked the slot for 8am without checking with the person who asked for it at 1pm is a bit unreasonable.