Certification for my film trailer

The certification of my film is going to be a 15. This is because of the bbfc guidlines  (http://www.bbfc.co.uk/sites/default/files/attachments/BBFC%20Classification%20Guidelines%202009_5.pdf), say that the language used will have to be a 15 as its too rude and/or constant for a 12A. I will also have a bit of violence in my film, although it will be funny for the audience, it still doesn't meet the limitations of a 12A. During my research, I've found that most 15 comedy films have a U or a 12A trailer so they can advertise their film in all screenings to attract as many people over 15 as possible. I am considering also using this tatic with my film trailer, but doing this, I will need to make sure I don't use a lot of bad language or dwell on a lot of violence.