No worries mate. I'd say the key is to try to stay as calm as you can (not easy I know) and avoid confrontation. In my experience there's not much point in trying to be nice about it and talking to them - mostly it's a waste of time, and it just gives them a target when the police/council do come calling. Keep it anonymous, and if anyone does accuse you of complaining, deny everything!
With regard to the noise, start to keep a diary of what you're hearing, when, and for how long. When the Enviromental Health Officers turn up, it will be useful evidence. Don't do the English thing and underplay how badly it's upsetting you, it's important that you show them how much of a nuisance it is.
With regard to the dealer, try crimestoppers, and if that doesn't work PM me. I'm not a copper, but I know a fair few and I can pick their brains on this for you if needed.
Last option might be a complaint direct to the housing authority/landlord (if known), some of them are reasonably clued up about this sort of thing, and they will bounce out their worst tenants if they can.
I know from experience how grim it can seem - don't feel obliged to tolerate it, but also try to accept it can take a while to sort out. It can be done though. Like I say, PM me if you'd rather take this offline.