Our playgroup went through a similar type of problem when the school wanted to merge with us. We had 8 staff then, and they wanted to give new terms and conditions, changing from term time to year round working, and reducing weekly hours etc. In our case we were told that they must offer equal or better terms, not reduced terms, as the post holders were already in the postions.
From what I remember, if you take a new position, it doesn't necessarily have to be under the same terms as a previous person had doing the same role. If, however, you applied for the post, and was officially appointed, then they reduced the package that they were offering, I think you have a right to complain. Maybe you would be best taking legal advice - some solicitors offer free 30 minute sessions. You may find this website helpful
http://www.berr.gov.uk/employment/em...page16161.html I think the variation of contract section may apply.
How is your committee organised? In most cases people running committee-led groups have no previous employment experience and they may be unaware that they cannot just change terms "willy-nilly". They may have seen it as a way to save money, without realising the consequences!