What is the link between British Social Realism themes and the real world?

The themes that are portrayed within British Social Realism films are very similar to the issues we are experiencing in the real world. For example in the real world there are young girls drinking alcohol, getting drunk and then have sex or get raped by guys taking advantage. Similarly in "Fish Tank" the main character, Mia is drunk and then has sex with her mums boyfriend. This reaction would be more shocking in real life than in the film, because the film itself is fictional whereas in the real world it has actually happened. The British Social Realism films are inspired by these real life events and are emulated into a film to make the audience aware that these issues can happen and has happened before in the real world.
What is unique about how themes are explored in British social realism films?

The themes in British Social Realist films deal with violence, relationships, sex, politics, isolation and many others. They are unique, because they all relate to the real world. The themes are explored differently between British Social Realism films and Hollywood. For example in "Nil by Mouth" the theme of domestic abuse is shown when the wife is brutally abused by her husband. This is a shocking scene that will startle the audience and you wouldn't see this in a typical Hollywood film like "Saw" which has a lot of violence and torture in the film, but audience still see a more positive reaction towards it, because they know its unrealistic and made for entertainment unlike "Nil By Mouth" which is portraying real world issues.
Is there any themes which are essential to all British social realist films? What are they? Why are they essential?

There are a lot of important themes that are essential in a typical British Social Realism film that make Britain as it is today in the modern world. The most common themes we see recurring are violence, relationships, alcohol and sex. These are essential, because the British Social Realism films are emulating real life problems and these themes in particular are what makes most of the teenagers in this day and age and is a growing part of British culture. "Kidulthood" is a very good example of this as it portrays all these main themes. This also creates a realistic, verisimilitude story-line for the audience.