We had similar at my old company. Plant workers were unionised, got to negotiate with management re pay and conditions and were very well compensated compared to non-unionised plant workers at other sites within the company. I was a lab worker and we were considered to be separate from the plant, and I couldn't get enough people to join a union so we could be recognised. As a result, we got shit pay rises and our flexi-time conditions were gradually whittled away. Everybody moaned and bitched, but no one did anything- I even arranged a meeting at a local pub with the union regional rep, no one turned up. Dicks.