You coild do public services btec but i know loads of people that say its a waste of time etc
Ive got a few friends going in the police, most have done:
Sociology, Language, Religous studies and sport science
why i hear you cry:
Sociology promotes knowledge of society, how it works
Language is good for communication, plus give you a head up etc with extra skills
Religous studies promotes knowledge of religons, ethics and how they live/worship- cultural awareness
and sport science too build up fitness!