Hi,
It's all about the Aptitude tests. Try this place
Cockpitweb: pilot aptitude test,Pilot computer test software,numerapt,numerical reasoning, psychometric test, mathematics,job application,pilot recruitment,IFR Training Software, ATPL Pilot Training, Pilot Training flight simulator, aviation training it could be well worth the investment. Practicing keeping the dot in the middle, catching the dots, instrument interpretation, etc...
When I went to OASC the word was that you needed above 130 to even get a sniff. In fact one guy on my selection board was applying only for a ground branch (logistics/supply?!?!), he scored around 160 and the selection officers practically begged the guy to swap his application to include pilot.
Best of luck
S&S