I suspect Megan was geeky at school looking at the pics and her father paid for the surgery. I suspect there is a back story there, potentially of bullying or something.
Remember when Laura and wes were having all the arguments, and she asked Ellie if she liked him, wes said something about he was scared to say the wrong thing. He got a rabbit caught in the headlights look about him. Jacks got that same look going on.
And yes kaz kept checking the door to make sure no one saw her pushing Idris to thr new girl. Laura was more open, she just butted in when she was saying how handsome Alex was with "but have you seen the new boys" . In fact she did it a couple of times untill she was heard.
I can't think why they wouldn't want Alex and the new girl to couple up. Unless as said, they think the couple may then become competition to them. Alex and the new girl seem way more suited to each other than anyone else who has been in there.