My take on the Millie-Liam situation. I think she's wrong to take him back (which inevitably she will). What he did, on the face of it, kissing another girl, sure it's not the end of the world. Others have done more/ worse. But it was clearly a big deal to Millie, we've seen her in tears being really upset - and she doesn't seem like the sort of drama queen who would get that upset unless she really was hurt.
So what's Liam's response to it been? He's hung around like a bad smell, made some inappropriate 'jokes' and various half hearted efforts to show his interest, basically by saying he's interested. But what thought has he shown for her, for how upset she was? What has he learned from his behaviour? I think precisely nothing. He was off kissing Lillie simply because he could, and because he thought he'd get away with it, and I guarantee he'll do the same time and again once they leave the villa (if they stay together).
That said, I get definite cheating vibes from Jake too, if he got the opportunity and wasn't too busy trying to win!