First of all congratulations on being selected for FC and good luck on IOT.
If you apply for re-selection following IOT, or even during professional training your chances of being re-selected for Pilot/WSO are minimal.
A pass in Pilot aptitude is no longer good enough due to the competition out there, it now has to be quite high to be selected.
They are only taking approx 30 Navs a year now and again the aptitude scores have to be competitive as well - and think about whether there is a long future in the Nav (WSO) world - (beyone ISTAR platforms!)
If you apply for re-selection you are likely to be offered just your original branch of FC - as has happened in the past to other officers.
Don't apply for re-selection whilst on IOT, wait until you have your commission, and are holding etc.
I am sorry if this is a grim picture, and not the answer you were looking for but just remember - if you don't ask - you'll never know what could have happened! If you want more info on re-selection for Officers look here :
RAF Re-branch
Good Luck!
BigGrecian
Wow - been a few replies whilst writing this - OACTU (Officer and Aicrew Training Unit - to incoporate Airmen Aircrew initial training who now share No 1 Mess with IOT cadets) has replaced DIOT now as well.