Visit CAB, maybe the landlord isn't even aware of it. If you're concerned about the old man contact the Social Work Office to pass on your concerns! Or phone the council's loud noise people, dunno what they're called - if they feel that there's more than just loud noise they have a duty to pass that information on. The Police will be keeping the info about the 'suspected dealers' to themselves because that'll be coming from intelligence. If things go wrong the only thing you can do is contact the Police. I can't help but put my Social Worker hat on, and if these drug users have children contact Social Work. Info can be passed anonymously.