As already been mentioned where wild guppies originate from, wild type and wild guppies have also been introduced within Europe. This would be in artificial thermal water bodies. This could be in free nature or basins. But no matter wild type (fancy guppies reverted to wild type) or wild guppy, we're talking about "feral populations" in this case. Most of them are Poecilia reticulata. But even Poecilia wingei has been introduced to these non endemic locations.

Above: Locations where wild type and wild guppies are to be found in Europe.

Illustration above & below courtesy :

Paper: European thermal waters as hotspots for aquarium dumping: insights into feral guppies and other pet-traded species from Southern France