Actually liked Simon in this! MINOR SPOILERS!
I hated his character in the show and the last film, he's simply not believable as a human being.
In this though he's actually one of the better characters, he has some genuinely funny lines/scenes and plays the groups "straight man" way better than he does in the show. His sub plot is believable (even though Lucy's character is OTT) and his reactions to her are amusing and authentic, especially at the end ("****ing brilliant!"). I didn't like how he ended up with Lucy in the last film (the way he was around her I'm sorry but it would NEVER happen) but it's perfectly understandable that he would be the only one still in relationship. I loved how he has actually developed into realising that a girlfriend isn't the be all and end all and that his mates are more important.
Overall good job Joe Thomas! Never thought I'd say that.