Been using my annual leave for Camps etc etc with the Reserve since I joined.....Seemed a cheek to kick the arse out of it and has helped my relationships with co-workers as the fitting in side of things. It did not help the case for extra paid/unpaid days when a fellow member of staff from the Cold war bar fly brigade of the TA was caught twating about when he was given leave to go to camp which he did not bother to attend.
Always though it was the price i paid for it even though i work for a local Gov.
End of the day as posted before the Reserve pay wont pay all all your bills unless of course you on ADC or FTRS.
On a lighter note the support i got while mobilised ( A Few times now) was excellent.
I would speak to your union rep, employers cannot just change T&Cs on a whim, there has to be consultations with the unions in your place, which has to be agreed with said unions. If your not in the union well you could just have a quiet word with the shop steward.
The OP is describing a change in company policy, not his Ts&Cs. Unless he negotiated additional additional leave into his contract, there is no contractual issue. I have no fcucking idea where you work, but there ain't no shop stewards in many private sector companies and very few businesses agree contract terms with unions.