No, and 'Britain' wasn't importing it into China. It was imported by merchants that were British, American, Indian, and Chinese. Neither the Royal Navy nor the East India Company imported opium into China before the Opium War, because it was technically illegal, despite usage being commonplace. Independent traders imported it, and handed it off to Chinese smugglers before it reached China, because foreigners, outside of some very small enclaves, were not allowed into China.