Jersey - well done for applying to University. We need lots of bright young things like you to try to make the world a better place in the future.
As an (ex) university lecturer I would have loved to have seen some of the suggestions on here on an application!! Haha!
On personal statements just keep it simple. Say what you want to study, what you like about the subject(s) you have chosen, why you think this is right for you, with examples from academic areas and outside of school as evidence of your potential. Mention transferable skills like teamwork and problem solving gained through school societies, clubs or work experience etc and, briefly, outline your hobbies and interests.
If you are applying to Newcastle University don't mention being a Sunderland supporter.
Also make sure you ask your tutor from school to read and help you refine your PS before you send it off. Also have you looked at the Student room website here:
http://www.thestudentroom.co.uk/wiki/Writing_Your_Personal_Statement and here for examples:
http://www.thestudentroom.co.uk/wiki/Personal_Statement_Library
But remember DO NOT copy anything verbatim from these sites.
Let us know how you get on. Best of luck.