In my view if its TUPE or not the same applies, need to give three months notice to change an employees contract, unless you agree the change.
If you disagree to the change you can put it in dispute.
This should be dealt with by your full -time Union Officer not by what someone has said down the smoking hut
If it is a TUPE transfer the employer will still try and get you on a new contract but remember you do not have agree depends if you have any B
ks or not !