Due to the number of slots available at IOT, especially for pilot, the RAF can afford to be choosy. Consequently, the chances of getting a letter saying 'Well done. You're in.' are slim. If you are being held for 'the sift' then you have probably done reasonably well, but OASC are waiting to see if anyone better, and more competitive for a slot at IOT, comes along. If you are unsuccessful this time they may put you in the sift again.
Unfortunately for those aspiring for a career as a Service pilot, it is most definately a buyers market.
Good luck, anyway.
kipper.