LadyDramaturg, I'm slightly unnerved by your response to my theory, but I think I'm just a naturally suspicious person. ^_^
I think Higgins's aggression, while it could be seen as symptomatic of other disorders, really just comes across to me as an extension of his theoretical Asperger's. In 'Why Can't The English?', he's failing to understand that other people have different brains to him that causes them to speak differently or (more importantly) just not care as much as he does. It could easily be played as exasperated lack-of-understanding instead of plain old fury - Higgins speaks like a proper English gentlemen, and because of the way his brain works, it would make most sense to him for everyone else to speak that way.
Demandingness, again, just a lack of understanding for other people's feelings. And he doesn't really feel any such need for Eliza, I see it as a combination of not wanting to lose his toy because it's HIS goshdarnit, and being genuinely flabbergasted that Eliza doesn't enjoy him toying with her life like she has no feelings.
I watched the documentary on
Blackadder last night. There's something really deeply wrong about seeing Hugh Laurie looking for all the world like House but talking like that skinny goofy Hugh Laurie who used to be in all the televised funny when I was younger. VERY weird. He'd need to shave and do his hair to not be utterly disconcerting as Higgins. And I bet he'd get a ton of people complaining about his "fake-sounding" English accent. XD
House = Higgins. The more I think about it, the less I see between them. O_o