Sam Duncan who plays Simon and Natasha Flowers who plays the Office Co-worker are in a relationship. It was just a coincidence that they happened to be in a montage that shows them during sexual acts.
Bree Whorlton who plays Jaqueline is Sam Duncan's second cousin.
You can see Bree's real Mum Fiona when her character is first introduced to her character in the park scene.
Verity Higgins who plays Jody (Mother of Simon),is real life mother of Emil Freund who plays Michael (Simon's antagonist).
The party scene was shot during an actual party. Most of the actors and crew were involved in the parties proceedings.