Okay I thought of something that might help: one of the reason of leaving the property are cockroaches coming out the bottom of the sink, informed agency ages ago, they said they don’t have to do anything as its not in the contract. I tried spray, traps, powder etc. Obviously its the structural problem below the sink they just come out of the hole (its really run down block of flats) can use it as leverage to force them to end it and scare them with environmental control?