Corrected entry: The human heart that Okwe fishes out of the loo early in the movie doesn't make sense. Sneaky's scam is passports for kidneys, not hearts (you can live without one kidney, but not without a heart). Even if the doctor botched the kidney removal and killed the donor, then tried to salvage things by cutting out his heart, wouldn't he try to sell it?
Corrected entry: Although the action takes place in London, the payment for the "goods" being sold on the black market is quoted in dollars.
Correction: The US dollar is frequently used as an international currency for all manner of illegal activities (there's a great deal of it available, and it's widely accepted). This makes more sense than the assumption that the English film's English writer doesn't know what the local currency is.
Correction: Sneaky couldn't have sold the heart; since he is selling kidneys, he wouldn't have had a heart recipient lined up to receive the heart quickly enough for it to be usable. Even if he'd found one it would probably not be successful, since heart transplants require far more extensive matching than kidneys, for which non-related donor transplants are increasingly common. So the best explanation for the heart in the loo is the simplest one: the kidney surgery was botched, the "doctor" panicked and killed the donor by taking out his heart, then tried to get rid of the evidence.