Please help! Chimney stack advice needed

[shredwood24]

Hi all, 

I moved into a downstairs flat last year, and noticed after decorating that there’s a wet patch on the wall in the bedroom where the chimney breast is (it’s boarded up) I constantly leave the windows open in the bedroom as if I don’t it stinks of damp. 

After mentioning this to my landlord he keeps telling me that it’s the upstairs homeowners responsibility to have the roof and chimney looked at in case there’s water coming in and causing damp upstairs. However after speaking to my upstairs neighbour he’s had someone out to look at the roof and he said he wouldn’t touch the chimney as it’s my landlords responsibility. 

I’m really confused as to who is responsible to fix this, as I shouldn’t really have to live in a flat which is damp, not sure what I can do as a tenant, and don’t want to upset anybody either but I don’t want to put my health at risk. 
 

can anybody point me in the right direction or give me some information so I know who is responsible etc? 
 

thanks so much :)