Fabbe92,
Let me see if I have this right. In August 2009, you can take a Class 1 Medical and a Psychometric test to hopefully get onto a state run school for free. The course will get you a PPL, night rating and 150 hours total time and it won't cost you anything. Is this correct?
Now to help you hear what people have been saying. You will probably grow up enough in four years to pass OAA or CTC's assessment, at least for self-sponsoring students. Quite a few people here think you have little chance of passing them now because of immaturity. By the way, you can't take them until you are 17 or 18.
Have you ever called or written to OAA or CTC? What sort of advice did they give you? How do you plan to pay for either of their courses, since their banks only lend to UK residents? The free option gets you about 1/3 of the way down the modular route. The remaining parts will cost you about 1/3 of what OAA or CTC will want.
To get back to your question on psychometric tests, have you tried Googling the word? How about looking on
Amazon.com: Online Shopping for Electronics, Apparel, Computers, Books, DVDs & more for books on psychometric testing for pilots? There are dozens of them.
They should not be called tests though, because there aren't any right and wrong answers. All they are trying to do is get insight into your personality.
Here's an online one you can take, but it is not aviation related. It will give you an idea what they are like. Just taking one should help you unwind a bit, as you will realize they are nothing to worry about.
Personality Test - Keirsey Temperament Website - Look for the free Temperament Sorter.