Gents, thank you all very much!
I've been using little spliced loops in bits of braided backing-line, with the end glued and trimmed so it will poke through the rings without snagging, but its a lot of faff for something I always lose, only to find, several weeks later, huddling with six of its kin in a reel case that I have no recollection of using.
I read of someone at an angling show in town in the sixties, who went in for a rod-threading competition; while the others fumbled about, he took out a matchstick and his penknife, cut a notch in the match, pulled the line into it and almost ran along the rod to win, easily. I suppose I could pre-cut a few, but they wouldn't go through modern, lined rings.
I'll give the various needle/stick and rubber tube ideas a bit of a test, too. Needles are a bit of a hazard when lost, though, but they can be retrieved with a magnet and some luck - if you remember to carry a magnet and feel you have enough luck to spare, but glass float-stems, cut down, and maybe a bit of a conical whipping to (try to) prevent the rubber snagging the ring and letting go, may work...
Onepoundfishingtackle have diamond-eye threaders in, so although it's the most expensive route, I've bought three, and a little Middy pole-bits-box to put them in; that should stop me scattering them about like confetti, and also give me a place for plummets, a few "trimming" shot and some float-caps, so I can put my main bits-box away and not keep getting up like a jack-in-the-box every five minutes, only to leave it out and knock it over (or get rain on all my hooks).
I have tried the pinched loop method, but the only way I can get it tight enough for long enough is to thread another bit of line through the loop and really heave; it's usually faster to free-hand it, for me.
One other idea is a bit of stiffish tubing - equipment wire sleeving or kids' Scoubidou tube - cut off at a slant at both ends. Pop the line in one end, trap it with a needle (hmm..) and thread the other end through the rings.
It appears, though, that my best chance is to get-make a few proper ones and look after them better!
Thanks again!