25 years ago there wheren't many in Europe. I heard of birds bred in France, Switzerland and Germany. Only a handful founders probably. Some Swedish breeder bought some at high price (€2500 p) and where quite successful. They even appear on birdmarkets today (with CITES papers).
BTW. There are also some Ouvea parakeets in Europe. Hybrids with Horned occur unfortunately with more red on head and the Horned's crest.