It sounds to me like that sealed up fire exit is required and should be re-opened.
Otherwise there is, (compared to national benchmark standards), an excessive travel distance for a single exit and the creation of an inner room situation.
All workplaces require some means of raising the alarm in case of fire. This may be anything from a shout of fire to a full L1 alarm and detection system conforming to BS5839 part 1. The design and specification depends on the level of risk, and in simple terms depends on how much time is available to make a safe escape from a fire in the building when compared to the rate of likely fire growth and the time it will take to detect and respond to a fire alarm. If a fire occurs in the outer room persons in the warehouse may be trapped?
Fire detection can be a compensation for extended travel distances and inner rooms but only within reasonable limits, 38m in most situations of this type would be pushing it too far. Sort out the means of escape then consider a suitable alarm system appropriate to the residual risk.
Who has done the risk assessment- I would ask them to review their findings and ask them if they are happy for you to confirm their findings with the fire authority.
