Cadets do not really enter the holding pool. Generally, training will be uninterruped (save a couple of weeks here or there) up until the type rating stage. I have heard of people waiting two or three months to start a type rating course, but my understanding is that this was people who were holding out for a particular airline.
As yet, no cadet who has passed all stages of training has failed to be placed with an airline. I'm pretty sure that the same goes for every ATP pilot who has passed the AQC and entered the holding pool.
I cannot comment on how employable one would be with a self sponsored type rating and some hours paid for on type, but I would venture that the chance of getting a job through the CTC cadet scheme is much higher.