HO, Many thanks for your concise yet complete answer.
In a strange way I think the recent threat of IA from BAA union members, which included RFFS and Ops shows the way. BAA management had extracted more and more from less and less over a number of years and clearly thought they could go on ad in finitum. Although the vote was marginal, middle management lost courage and batted the problem up all the way to Spain.
The fact that the ACAS talks lasted but a day and quickly reached an amicable
settlement should give VS some comfort.
I hope you and your colleagues take a stand as I'm sure, given the facts presented here, you will prevail.
Best wishes
Sir George Cayley