Hi, cocteauUK. If the property is leasehold, then there's quite probaby something in the lease about proper disposal of rubbish, upkeep of communal areas and so on. If you're a leasholder too, it's probably the same lease as that of the other flat, so check through it to see if this is the case. You then have something to go the the freeholder with to show that the tenants are breaking their lease. This is my feeling anyway. I'm no expert. The CAB would be able to give you sound advice on this.