It's probably best not to tell people before you start your training. If it is a problem then it will become obvious to the QFIs. Very few young people these days have any need to opportunity to use or develop their skills.
If it does show though whilst sat in the hot seat (and that's when these thing do tend to flair up) then you will find Nav difficult and possibly some approaches and fuel too. The actual flying shouldn't be too tough however.
Preparation is the only way to get around things like this, the more you do on the ground means the less you have to think about under pressure.
The aptitude test should flag something along these lines however.
I have heard that a number of people with dyslexia have very good spatial awareness however. So that could help with test scores.
Good luck with it though. Practise makes perfect.
