Illegal men's hostel woes

Hi, One sad excuse of an individual has converted a flat in an apartment next to ours into a men's hostel aka pigeon coop. It is completely illegal as they have no indication that they are running a business there. The EB connection is also not commercial and they have none of the requirements for a hostel.

Worst is the occupants - They treat the whole apartment like a bar. Expect this hostel now there are no other residents there so these guys have literally turned the terrace into a garbage dump with half eaten packets, food covers and bottles thrown everywhere. It's a horrible sight.

Neither the occupants nor the guy running the hostel cares to what we neighbours have to complain and just abuse us. How do we file a complaint against them?

As with any normal scared citizen I'm more afraid of the authorities like police. Is there any way to file an anonymous complaint?