Another issue with cotter pins for French-made cranksets is that they're narrower than English. Here's the relevant paragraph from Sheldon Brown: "The diameter of the round part of the cotter tends to be standardized according to nationality. Most use 9.5 mm, including British, Asian and most German bicycles. French and Italian bicycles used 9 mm, or sometimes 8.5 mm."

I learned this while trying to replace the cotters on an old Peugeot. However, I don't know if an old Stronglight cottered crankset from a vintage Raleigh would have French or English-sized. I'll have to dig around in the parts bin to answer that question.

Neal