There are things in the movie that I noticed, but could very well be reading into the movie far too much. I just wanted to get second opinions.
1. When Shaun goes into the corner market, he first picks up a Diet Coke and replaces it for a regular Coke. Later, when he must prove himself to Liz/get her back, he replaces the regular for diet. This echoed the "going to the gym" demand Liz had previously made.
2. One of the albums in Shaun's record box, The Stone Roses, has a track called "Bye Bye Badman". At the time this album was released, Shaun would have been 14, and it seems like a fitting track for him to listen to while dealing with his new stepfather who he wasn't too keen on.
3. Shaun and Yvonne obviously have a past. I couldn't help but think that maybe Liz knows her, too or possibly "stole" Shaun from her after they met in Greece.
4. Liz seems to be a faded version of a hip young adult. And judging by Shaun's interest, he was like the dorky guy who got an awesome girlfriend eventually. But, because of his routine-driven life, she is losing that spark she once had.