I have found what, on the face of it, appears to be a source of reasonably priced good quality gold thread (not real gold!). The Lady on ebay who sells it claims that it is vintage from a factory in France that has since closed down and she herself acquired them from an antique fair. They were apparently destined for use in restoration work and for civic uniforms and banners.
I have bought 4 reels and will be happy to report back on whether they seem fit for purpose, or if I have just been conned out of my money!!