This depends mainly on what the written statement of employment particulars and your employment contract say.
You must be given a written statement of employment particulars on or before your first day of work. This should say clearly whether or not the handbook and staff rules are contractually binding and form part of the contract of employment.
Even if the written statement says nothing about whether the handbook is part of your contract, some of the rules in it may still be contractually binding in some cases.
Your employment contract also contains some important implied terms, including a general duty to obey all reasonable management instructions and a duty on both sides not to breach the duty of trust and confidence in every employment relationship.
Any rule or procedure that is part of your conditions of employment is a contract term and cannot be changed by either side without agreement. Where a trade union is recognised in the workplace, the change will normally be negotiated through collective bargaining.