Everything you've been taught about drugs is a lie. Everyone does them and no they're not just for chavy people in council estates, more often than not it's your silver spooned Russel group undergraduates at the likes of Leeds, Newcastle, Manchester etc who do coke and MDMA several times a month.
Get used to it, they're the norm in numerous times of offices and even among the people who run the country. Never forget, David Cameron had relations with a pig while high on coke.
If they're not to your tastes steer clear but don't snitch unless you have major reason to