Oxycontin is available in Europe, including in the U.K. Many people take it for pain with no problems apart from the medical dependence that comes with regular use of opioids.
The problem in the US was initially due to the time-release mechanism not working properly. Drug companies refused to allow doctors to permit 8-hourly dosing instead of the recommended 12-hourly dosing. So the patient would feel fine for say, 6-9 hours, then be in agony until the next dose. Drug companies insisted the mechanism worked fine and told doctors to increase the dose. So a patient who was taking 10mg twice a day would have their dose increased to 20mg twice a day, instead of 10mg three times a day. But they would still be in pain between doses. Doctors gave higher and higher doses without the pain being relieved consistently - no wonder patients became addicted!
In Europe now, doctors who understand pain management will switch a patient to 8-hourly dosing if 12-hourly doses wear off too quickly and breakthrough pain is not controlled by the sister drug Oxynorm. This allows patients to be stable on lower doses. Many stay on the same dose for years. Just because it is a street drug, it doesn't mean it can't be used by patients who need it. For many it has fewer side effects than alternatives such as morphine.
Ketamine is also used in pain management, both in emergency medicine and for long-term management of chronic pain (by regular infusions). It is also used for treatment-resistant depression, often in the form of a nasal spray.
So many myths floating around!