Aha! Yes. American Apparel has been on my list as somewhere I intend to check out. Intimissimi was a dead loss for non-padded stuff last time I tried it, but perhaps their stock has changed or I was in a small branch, as that was donkeys aeons ago. Tezenis I haven't even heard of, so will check them out.

Thanks for the recommendations :)

I'm not so fussy about fabric, and I would say that I quite like a little decoration. Having said that, my "quite plain" was interpreted by the last underwear salesperson as meaning "only three of lace, ribbons, sequins, beads, diamanté, spangles, buttons or ornamental mammoth-tooth carvings" so maybe "as plain as possible" is the way to go!

(Edited to add missing "not"!)