Listening to these songs reminds me of the themes of Fake:
Do I Wanna Know by Arctic Monkeys
Confide in Me by Kylie Minogue
Aaron’s band, Fake, is a combination of a few bands. Listening to this will give you an idea:
One Armed Scissor by At the Drive In
A few songs that make me think of Kath:
Girlfriend by Avril Lavigne
Strong by London Grammar
Chasing Cars by Snow Patrol
Love Story by Taylor Swift [this song reminds me of the stories she makes up about the antiques she finds]
And since we only know Sebastian through Kath, Green Eyes by Coldplay perhaps describes him, and I think he’d listen to bands like Boards of Canada and Mogwai.
Some songs remind me of specific scenes:
I Gotta Feeling by the Black Eyed Peas would have been blasting out of Chay’s stereo the night of the dance.
Apologize by Timbaland featuring OneRepublic would be playing in the terrible moment when all the lies catch up with Kath and she loses everything.
Feel So Close by Calvin Harris and Love is Easy by McFly could soundtrack the end when they meet on the stands.