I shall have to think a little more about this one...
I already feel that my company thinks of me as just another number rather than a valued asset. I am right at the start of my career so if they tried to take the FS scheme from me now I would probably accept it and then leave ASAP. The fact that they were trying to take it away from me would just be the final straw - proving that they really do not give a monkeys about my well-being within the company. It is not something I would want to fight to protect by striking, because even if we won, I would not want to work for such a company. (Besides, you could be sure they would have another bash at it a few years later!)
I think it would be a different story if I had been working for the company for 10 years or more. Then I would stand my ground and fight... and I would certainly strike if it came to it. Saying that, if things continue the way they are in my company, I will not be hanging around any longer than 5 years anyway!
So I have not voted because it all depends upon the company's timing...