Medical professionals have always had a higher than average risk of opioid addiction. Popular lore says combinations like Pentazocine + Pyribenzamine was invented by lower level healthcare workers (as in the '70s Pentazocine was unscheduled the way Tramadol is now, and Tripellenamine/Pyribenzamine was a common Rx anti-Histamine, like Zyrtec/Claritin today). There is even one serial killer doctor addict who would prescribe large amounts of Rx Diamorphine to his elderly dying patients, administer a lethal dose, and keep the leftovers for himself.
An opioid addict is much different than any other drug addict, in that the compulsive use of opioids does not impair their ability to function as a productive member of society the way Cocaine or downers or alcohol do. Maintenance programs have proven that an opioid addict who is maintained on any opioid is going to be just as productive as any non-addict member of society.
The Swiss, Dutch, etc have Rx Heroin programs, but they have stringent requirements. You have to meet certain standards, consume your prescription Diamorphine in designated clinics no more than two or three times a day depending on the program, regular counseling, meetings with healthcare workers, etc.
The British Rx Heroin program is much, much more lenient. Although the law in the UK says a British doctor who prescribes IV Heroin or IV Methadone to a patient for maintenance/detox has to be a registered specialist (like the Buprenorphine guidelines in the US), any doctor can prescribe IV Heroin/Methadone, Diconal, Dilaudid, any narcotic for pain. There have been a few court cases regarding regular doctors prescribing narcotics like Heroin/IV Methadone to addicts without being a specialist. Either way, the onsite consumption, counseling, etc does not exist in the UK guidelines, you go to the doctor, he prescribes Diamorphine ampoules, and you consume at your leisure.
I don't know if you have to be a citizen of the UK to get a script for IV Diamorphine maintenance. There aren't many Rx Heroin patients out there in the UK though, it's mostly oral Methadone and in some cases IV Methadone. But it is possible, and much less stringent than Switzerland or the Netherlands' requirements.