Your implying that the union and the employees interests are the same, my point is that, that is not always the case. From experience. Anyway this is getting off the point. Ypur advise to get an advisor is good and might save money in the long run.
Unfortunately this is true sometimes, and I've seen it happen. But then it's up to the members of the union to make it work for them.
OP,I've just thought of an advantage of dealing with a union for you. If there are, say, 7 staff in the union, you only need persuade 4 of them to agree, and the other 3 are bound by the union decision.