The law states that you must provide a written emergency plan. This will be specific to the workplace and will detail the pre-planned procedures in place for use in the event of a fire.
This must include the following features:

action on discovering a fire;
warning if there is a fire;
calling the fire brigade; including unique reference numbers (URN)
evacuation of the workplace including those particularly at risk;
power/process isolation;
places of assembly and roll call;
liaison with emergency services;
identification of key escape routes;
the firefighting equipment provided;
specific responsibilities in the event of a fire; and training required.

Remember to test your emergency plan by practising it with your employees, and if necessary discuss it with your local emergency services or Fire Safe Solutions.