It's quite a puzzler your newly-found French item, Kim, and I reckon that until and unless you manage to find something on the down-tube, you never will really know what you have there.
The head-tube transfer with its "Worlds" bands is a very common sight in France, and you often find similar tbanded transfers on the seat-tube. If you looked through my collection of French frames you would find at least a dozen frames with similarly designed transfers, almost as though the same decal manufacturer supplied several bike shops..and that might just be the case...variations on a theme, so to speak.
The "brands" that I have with "Worlds" decals similar to yours are - "REBOUL" of Montelimar, PREUSS, LAURENT, GUILLOT, JP , JAQUERTY, and one or two others. The interesting aspect of these barnds is that some such as Reboul and JP are simply shops who have frames made for them while others such as Preuss, Laurent, Jaquerty..make their own. It has to be admitted that many of these quality transfers do set off an otherwise inferior frame..not that I am suggesting in any way that any of the brands mentioned above is inferior. But many has been the time that, across a dusty forecourt of a "brocante" shop I have spotted the highly coloured decals of a "racing" bike, only to discover after rushing across to claim my prize, that the quality hand-built of my desires, was in fact just a gas-piper from one of France's larger producers and "Branded-up" with great-looking decals.
However, Kim, I think that your frame has all the possibilities of being from a good artisan frame-builder, rather than a manufacturer such as Gitane. As has been mentiond there is some delicate drilling of the lugs..these are not pre-stamped windows in the lugs, and the builder has chosen quite large holes that run pretty close to the edge of the lug points...perhaps not the work of an amateur. I had thought from the verbal description that the frame might have been from my friend J-M Duret, who uses often a drilled motif..but his pattern/style is different.
If the frame had been factory-built I think that there would be every likelihood of the seat and chainstay ends being domed and slotted rather than straight cut-offs. Yours are reminiscent of either some Columbus stays as they come out of the box or of longer stays that have been shortened, possibly even by having the dome cut off. The seat-stay top-eyes are also too neat to qualify for a mass-produced type bike..there's been a file onto them to sharpen up the profile A mass-manufactuerer would probably have had a machine -pressed shape at that point, formed from the seat-stay tubing rather than a hand produced and plated-up top eye. The other feature that convices me that the frame is a hand-built/small workshop one if the curious choice of fork crown. This crown does not seem to fit the design of the lugs..and it appears to be pressed rather than cast or forged...possibly something from the Nervex or LG range. Had the fork been a Gitane,or Motobecane, or other similar large manufacturer, I think the crown would have been one of the Wagner range with a Vee or chevron milled into the top face.
I don't think this analysis will help you identify the frame but it might make you look upon the frame with more affection and curiosity. It certainly looks quite a good frame.
Norris Lockley..Settle UK