British Board of Film Classification

All classification decisions are based on the BBFC’s published and regularly updated Guidelines. The Guidelines are the product of extensive public consultation, research and the accumulated experience of the BBFC over many years. They reflect current views on film, DVD and video game regulation. In the most recent consultation over 8700 members of the public were asked for their views on classification – including consideration of issues such as language, discrimination, violence, sex and drugs in films, DVDs and video games, parental concerns about younger viewers and recent BBFC decisions. The Guidelines also take into account the various UK laws which the BBFC must consider and apply when making classification decisions. The Guidelines are updated every four years and the current version was published in June 2009.
Here is an image taken off the bbfc website to show how they rate the certificates for certain movies:

A 12A certificate means that you are able to go into the cinema under the age of 12 as long as you are accompanied by someone over the age of 18.
The films won't be able to show graphic scenes of sex or violence. But they are much more graphic than the PG and U-rated films. The British Broad of Film Classification (BBFC), will allow some nudity, but it will have to be brief and discreet. Also violence must not show much detail and must not have much emphasis on injuries or blood and swear-words must be rare and justified. Films such as, Pirates of the Caribbean, Harry Potter and the Deathly Hallows and Yes man.

No one younger than 15 years old is allowed to watch a 15 film.
Drug taking can be shown but it must not promote drug misuse. During a horror film, strong threat and menace are allowed unless they are sadistic or sexualised. They have to be careful that what they show doesn't get imitated e.g. Hanging or suicide. They aren't allowed to show it in alot of detail. They can also used strong language as long as it is justified. For example The uninvited, Good luck chuck and Love and other drugs.

No one under the age of 18 are allowed to was an 18 rated film. This is because the film could consist of extreme and detailed violence and illegal drug use which could cause harm to public health or morals. Also extreme horror would be under an 18 as it could cause people alot of phscological harm and could possibly scare children for life. For example In Bruges, Saw3 and Jackass 3D.

After consideration i would label our film as a 15; because it would contain some strong violence and language.