Allotment Dilemma

Hi guys, I'm not sure if this is the right place to post this but here goes: The site I have an allotment on is due to become self-managed. One of the new rulings that the new committee (they're the same old committee just with new powers) is trying to impose is that plots can only be 5 or 10 rods, which is fine for newcomers, however, they wish those current plot holders who don't conform to their new ruling to change their plots. I have 7.5 rods which was issued to me from the council, I didn't ask for this size I was just given it and was very grateful and I love it. I am now being told to either give up 2.5 rods or take on a further 2.5 rods and obviously the rent that goes with that. I don't wish to take on the extra space and I also don't want to lose any of my current plot. My question is: can they do this to existing plot holders? Does my agreement/contract with the council mean anything now. Any help will be appreciated.
Posts
If a business changes hands the existing t&c's would have to apply for a set period at the end of which new negotiations would take place. If your contract states a size I don't believe that they could change your plot size without your consent.
Thanks MuddyFork. I was originally told that the plot I've got could only be 7.5 rods due to a brook running at the back of it but I haven't got that in writing and the person next to me has extended his to the full 10 rods, that's probably where they've got the idea from. Any idea how I approach them with this?
I would get the other holders together and get their view's-surely it is run for the benefit of the users not the committee?
I wonder also about the practicalities of taking away part of you plot?- are there established paths in between--is there going to be an odd 2.5 area that no-one wants?-how can you extend into a brook?