Where do you live? - I would suggest getting to know your local force, go on the internet and find out who your local Beat Officer / Neighbourhood team is. Contact them (you can do this via email now, with most forces, and arrange to meet up and have a chat.
It might be an idea to go on a "rida-along" - this is where you get to go out with a Police Officer and observe them for a day/evening.
If you are dead set on becoming a police officer - you should be able to download an application form on their website.
You can also get some insights by going to this website;
How 2 Become a police OfficerHope this helps