Hi Ian - not much joy here, I'm afraid. I can't find anything about Gexair.
F-HECO, according to Airframes, is used by Smart Aviation of France (not, presumably related to the British or Egyptian Smarts), and I can't find their logo eiither (shame - they have an ICAO code of SMV). Fortis Lease France appear to have been taken over by BNP Paribas and are now called (or possibly are part of) BNP Paribas Lease Group. I've done that logo for the sake of doing something, but if they are indeed just the finance company, this logo won't really be relevant.
F-HEKO - C525 of Smart Aviation France / BNP Paribas Lease Group
I can, however, find the logo for Air One Executive - it's in reply #71 in this thread ;-)
Rod