I just want to share my (limited) experience with CAST lists, simply to wish you that new CAST selection procedures will have improved when you get to be in a list. I'm in two CAST lists since 2012, Educators and Translators, two professions in which I have 7 and 13 years experience respectively. In all these years since 2012 they have only called me twice (once per list) and it was (oh maybe by chance?) during a period of time where I happened to be living in the cities where they had positions.
Both interviews had these points in common: 1) the panel had not read my CV; 2) they needed people with different skills than the ones I could offer. I know number 1) is true because if they had read my CV, they would have realised number 2) and thus they wouldn't have called me. Believe me, it's very frustrating to go to an interview and realise after a couple of minutes that the panel is wasting their time with you and, more annoying even, that you're wasting your time with them instead of be looking for a job where you can really be useful. This kind of scenario does not happen in the private sector! In the private sector they won't call you unless your skills fit the position! At least they could have described very well the set of skills they were looking for, so that I could call the interview off if I felt I was not meant for the job.
Now that I know the real, specific needs of the departments I was interviewed for, I can say that the CAST exams were very unrealistic, and even useless, back then in 2012. Just to give you an example: for the CAST Educators they selected secondary school teachers such as me, but the truth is that they only need people who can work with 4-12 year old kids. Really? Secondary school teachers? In which EU country do they have 4 year olds in secondary schools? So the first stumbling block these poor people have in the selection panels is: they don't have in the lists the people they need.
Or maybe they do, but they call first the ones who live in the same city, and in that case they don't bother reading their CVs, as it happened to me!
Looking on the bright side, as always, I used the chance to learn from the experience and practice my communication skills.
I just feel sorry for the poor panel that wasted their time and mine.
Good luck with your CASTs! Please learn from my experience and always always find out, before a job interview, the EXACT set of skills they're looking for.