Nattyboh,
I just recently interviewed. I received a CJO. All I did to prepare for the cognitive test was review the test descriptions that are out there floating around. Knowing what they test is like helps you know what you are up against. After that I downloaded all kinds of mental games available on ipad. Memory games and reaction games just helps get your brain active. The tests are not that tough. Before each test you can practice it till you feel comfortable. Read the direction well do the practice and you'll be fine. Hope this helps