My two cents on the whole thing (having just caught up, and then found this thread!)
Sophie - my god I can't stand her. Her voice is probably the most irritating thing to listen to ever, along with her yelping hyena bark laugh that she emits every few seconds. She's also just completely full of shit, and arrogant into the mix.
Leanne - seems a nice enough girl but her constant 'omg I can't look/omg I'm so embarrassed' cringing is annoying. What did she think she was on the show for? She's also clearly territorial, she was fuming when Mike's heart rate went up more for Sophie, and was cat calling one of the girls (I forget who now?) telling them to 'move on' from Mike. It was just a game? But that was brushed over in light of the new girl coming in - though I find it odd that such a big deal was made of Callum & Connor's heart rate going up for Rebecca, but not Mike for Sophie. I also think her wig is really bad, and she looked far better the day she just had her natural hair.
Rebecca - I think is prettier without make up although looks a lot older than 21. She seems on the one hand fairly down to earth and straight, but I didn't like her making the point to Shaughna straight away that both Connor and Callum had been complimenting her on the date and saying how beautiful she was - it just came across like shit stirring to me, and rubbing it in a bit with Shaughna. And whilst she has no loyalty to Shaughna, she made it pretty clear that she isn't bothered about upsetting anyone - seems a bit hard.
Callum & Shaughna - I like her probably the most of the girls, but she's definitely quite insecure which lets her down. Unfortunately I think Callum is only going along with it while waiting for someone 'better' to come along - he's made it quite obvious by his lack of reassurance to her (which I think is why she's justifiably worried) and he even directly said to Rebecca that it would take 'someone good' to turn his head away from Shaughna. Not a particularly strong statement really.