Some years ago a number of staff working for a major bank were told that there would be a unilateral change to their contracts - and were told they could like it or lump it - they were definitely given the impression that they had no choice but to accept the change or resign. Unfortunately for the bank in question the staff involved were their Legal Department! Every member of staff replied to the letter indicating that they did not accept the revised terms and that they would be continuing to turn up for work but "under protest".
http://www.direct.gov...onditions/DG_10037116
The bank found that it wasn't quite prepared for quite this level of dissent. They certainly didn't want to pay for mass redundancies nor did they want the bad publicity that a number of tribunals would have involved. (Nor were they getting a lot of advice from their Legal Department!)
Negotiations broke out shortly afterward!