I think I'm right in saying that quite a few of the bigger companies will put you through their own type rating regardless of whether you're rated on type. I'm now with eJ on TR with CTC and I know that a few of the guys here had A320 ratings before joining and were required to an eJ 320 rating. So a definite thumbs up for going for CTC/GECAT if able, who already train on behalf of these airlines in my humble (of limited experience) opinion.