You can't unilaterally change the terms and conditions of employment they should be consulting about this.
He can be bound by them if he continues to work at the company as it would be implied acceptance.
Is there a staff representative he can go to?
If there is no collective consultation process and no staff rep he should as a first port of call write all his concerns issues down and send them to HR stating that they are unacceptable. The more he can get to do this the better.
This may be helpful from ACAS
www.acas.org.uk/index.aspx?articleid=816
How can contracts be varied?
An existing contract of employment can be varied only with the agreement of both parties. Changes may be agreed on an individual basis or through a collective agreement (ie: agreement between employer and employee or their representatives).
An employer who is proposing to change an employee's contract of employment should fully consult with that employee or his or her representative(s) and explain and discuss any reasons for change.
Variations of contract can be agreed verbally or in writing. It is preferable for any agreed changes to be recorded in writing.
Where a variation in the contract has been agreed and the changes concern particulars which must be included in the written statement of terms and conditions, the employer should give written notification of the change to the employee, within a month of the change taking effect.