Hiya Sweety,
I was in BASSA at Britannia, and they were good. Heard bad reports about cc89. However, If you are in same co as me I think the company are only in discussions with joining cc89. Let me know if you have heard different.
In my experience it is beneficial to be in a union. For example I have heard that crewing can expect us to change our days off for duties if they so wish. Ridiculous

Without being in a union they can do what they like.