Yes. We even had people obviously shooting up and leaving their "business" behind one of my old workplaces.
It's very common these days to smell cannabis smoke in even very public areas (though there have been some more stop and searches I've seen in certain areas more recently) though thankfully less common on the buses than it was, especially the double-deckers and in winter when all the windows are shut.
Where I work now we have police warning posters up around and were warned about muggings when we started and advised to go out in pairs if we went out at lunchtime. Just down from me (into Moss Side) there are signs up saying undercover police are patrolling in the area and we get mounted police round patrolling sometimes.
ive seen them tons of times all over the place, strangely enough near grates a lot of the time but they are on the local park and in the areas where its common knowledge that a lot of the people living there use them..... it doesnt seem as bad as it used to be now though, maybe they are more careful where they dispose of them now (though i doubt they care where they chuck em) or maybe the drug use is dying out or they are ....