I think Luke and Demi quite like each other too, but more they are confortable with each other and could go there, it won't last a second in the real world.
Natalia and Jamie would be the first couple out if they got together. Jamie is an arse, and Natalia left her personality at home.
Shaugna is playing a game, she no way fancies Luke. And everyone in that villa knows it. Poor Luke is just trying to work out how to say no chance.