In a private company does a change of contract only become valid on the signing of that new contract by law, or can the company make its own decisions? I have a new contract in my work since I was forced to move to a different department but I have not signed the new contract, there is no suggestion that the existing one is invalid right now. I don't agree with the new contract and HR don't appear to be chasing me up on the new contract
Can yo give an example of the sort of changes to terms you are talking about- hours? pay? job description?
If they gave you the required notice and you appear to have accepted them by working in accordance with the new terms you may well find you have effectively accepted them