Hmm. Is there no way that you could become happy in your new home?
I don't think it's right to uproot the couple who have moved into your old house, to be honest. They will have gone to a lot of trouble to move (I've only done it twice, and it was very stressful), and it's not their fault that you aren't happy.
I don't know about social housing rules, although I doubt that you are eligible if you won a property - are you sure the information you have is correct? Don't the council do checks to ensure that people have the right number of points, or did you arrange the swap privately?
Even if it's right, it doesn't alter then fact that you moved willingly, and the HA has said you can't change your mind. I can't see them changing their minds, even if they have to evict the other couple - but you don't know what problems that will cause people who haven't, presumably, done you any harm?