If you are interested in exploring academic ideas beyond your A-Level courses and are in the Lower Sixth, please read the attached powerpoint and get involved. Prizes, kudos, and pleasure in writing await.
Oxford has a list of current essay competitions here: http://www.ox.ac.uk/admissions/undergraduate/open-days-outreach/events-students-teachers/resources-teachers/academic-competitions-schools-and-colleges
The RGS essay competitions database contains an enormous range of competitions: http://rgs.to/vncqe
See Mr Chevalier for further support and details.