Nested between the dim sum eateries, Asian groceries, and increasing number of betting shops In London’s china town, sits Opium. Deliberately unassuming, this is a address that also offers dumplings, but only as an afterthought to its concoction of cocktails. Each cocktail is elaborately mixed (with some often unusual ingredients) and beautifully presented (well worth it for the somewhat alarming prices). Split over several levels and dimly lit this is an exotic eastern location for true cocktail aficionados, or for a intimate first date…