Combustible material stored under a the only escape stairwell

[Mersey]

I have just checked an engineering stores / office. There is one way in and one way out their office area. Their office (6 staff) is on the 1st floor which they access via a  concrete staircase with two breeze block walls either side of the stairwell so it appears to be what I would consider as protected stair well. I went into an adjacent room to find out if there is anything stored underneath the stairs and found it to have an unlocked sliding door jam pack with old archive combustible (paper boxes etc..) Although it is a concrete stairwell I could see small gaps through it 10-20mm  in various location, there is a distribution board in this cupboard space too I'm unclear whether it is redundant. They do have an automatic fire detection system so if a fire was to start under the stairs then I'm sure the AFD would alert them before they were filled with smoke.

 

Is it just good practice to clear this area of combustible material or is in lawful due to it being a final escape / only escape stair well? I'm going to ask people to remove the files but if met with resistance I wanted to be able to challenge back, I'll try and attach the picture 

 

[AnthonyB]

If the understore store has the gaps suitably firestopped and has a fire door, then being concrete it could be used as a store, although there could be an issue if that is an active distribution board, also is it a metal or plastic board?