Generally it works well but there's an ongoing bugbear that he seems to think that I'm intent on taking advantage of him, specifically around things I need help with in the house. So...moving heavy stuff that I can't do on my own for example, or more recently some flat pack furniture I've recently bought that takes 2 to assemble. Tonight he's had a massive hissy fit about that....I'm taking advantage of him in asking for his help and no amount of ironing or cooking I might do in return will be enough to make up the balance
I lived almost exclusively with housemates for years, and I know exactly what you're talking about. It's more common in men I think, but I've seen it in women too.
It can be infuriating and hurtful. Sometimes men like this have mother issues. Often, but not always, their mother was overbearing or suffocating them too much when they were growing up. It's possible they have a very defiant nature that is mostly displaced too. There might be trust issues floating around in the background, particularly towards women. It could be a pervasive victim mindset (very bad news for you as you will be coerced into doing all kinds of things as your good nature, guilt, and desire to be a good person is used against you).
He may know exactly what he's doing. He knows you need help, he knows you're being reasonable.....but he simply doesn't care because he want to do anything for you. He can usually get his own selfish way by accusing others of wrong doing which allows his to get away with doing fuck all. If he does do anything, even better as he can present himself as a put-upon martyr for helping - win-win!!
With a man like this, requests for help or cooperation will be interpreted as you telling him what to do, you overstepping boundaries, you being controlling. They are unable or unwilling to see when someone is genuinely asking for help and someone truly domineering. You're going to feel like a bad person even for asking him to do entirely reasonable things. He will make you feel guilty for just asking him to pull his weight.
This is going to cause a lot of conflict once you live together. It's an irrational at worst, and supremely selfish and manipulative at worst. You just can't work in a team with someone like that because they don't know the meaning of the word (there's a lot of them out there in workplaces too). It's awkward, conflict-ridden hard work.