This is a good summary of the legal position from a reputable source (DirectGov).
http://www.direct.gov...onditions/DG_10037116
Woofgang has the right principles well stated. The consultation needs to be on an individual basis unless collective bargaining reprsentation exists at the place of work. Keep individual notes of what is said to you individually, and keep any correspondence the company sends with dates received.
At the end of the day, an employer can and will change terms if it really wants to, subject to giving contractual notice, but it has to follow a fair process - and that means consultation.
If it fails to consult, it means the process if flawed. The remedy from an employee's point of view is to resign immediately once the new contract is invoked and claim constructive dismissal at an ET, but do not do this without seeking advice on your particular circumstances as there is no way back to the employer after doing this - only the opportunity to extract money in compensation for the breach by the employer.