I used a website
www.einforma.com
which is a standard search engine for low-level commercial investigation in Spain.
It indicates that Euro C was founded near Barcelona (Castelldefels on the coast just south of BCN) but moved to Valencia around 2005.
The names of directors etc does not appear to show any strong correlation with the same list for Flightline.(One second surname in the Spanish double-surname convention appears amongst directors but hardly seems important.)
Indeed Euro C seems to be controlled by someone from the estate agency/ construction industry currently. Which might tell us something.