*edit I think it was the Netherlands
Yes, in Netherlands, Austria, Denmark... diamorphine programs do exist, but it's not a very common thing and probably only for nationals or at least legal residents. I think small eastern Euro countries like Croatia and Serbia have good hr facilities, also.
There are places like Norway and Sweden
I think that you mistake Sweden and Swiss. In the late there are indeed advanced harm reduction programs with morphine and diamorphine apart of mdone. Sweden is exactly the opposite, it's the most restrictive western euro country regarding drugs, their police even goes to summer festivals and randomly test peoples urine for drugs, go figure.. Greek laws aren't drug friendly, too.
I have considered Portugal as I believe "small amounts of anything" are legal -- ease of access I can not speak to ---- I may be too Irish pasty american to do well there.
There is a big misundertanding about Portugal and legal drugs. Drugs are illegal but you don't get arrested and legally prosecuted over small amounts, you just get fined with like 300 €. Spain is the same but fines are more expensive, like 400€. There are some differences, like Portugal, in some cases can force you to undergo treatment, and Spain may legally punish you if they catch you with drugs too often. That's what law says but I have never seen such thing happening.
Drugs are more or less accesible depending on the kind you want and the location you are at. But both countries are human to their addicts.
Of course speaking their (our) national languages and being dark eyed/haired helps, but you shouldn't have problems being an Irish american, there are a lot of blonde blue eyed dudes living their lives no problem. Only thing is that some foreigners live for years in Spain/Portugal and refuse to learn a single local word, cause they think that it's the local people who have to speak English for them. Such people lose people's respect and will be scammed forever, they get the worst drug avaliable at the highest prize possible, but they deserve it, if you ask me.