It's the floor, near an internal wall. Most likely is upstairs running along edges (path of least resistance and all that) but I don't want to get people in and then have to argue about insurannce, etc. I'd rather get it done by someone on the books already if you know what I mean?
If it is external water ingress - eg outside wall/roof then its the *Buildings Management Company's responsibility.
*out of a service charge ?
if you keep getting fobbed off go through their complaints procedure and then here..
https://www.ombudsman-services.org/sectors/property/who-can-we-help