Carlton did a number of Mixte frames, there are usually ones on ebay (Courette). There are gaspipers and 531 in the range, and, if you go for pre-1960 or post 1980 then you should get English threads.
These Viscount Sebring are pretty sweet. I bought one for my wife, and I rode it the other week. Great bike. The same set up as the men's version except the frame. IMG_2609 by Sooper 8, on Flickr
Raleigh Royale/Royal Lady 531 are/were nice bikes with the metalic sparkly blue paintwork, the older variant with orange equally so.
Dawes Londoner 531 was a nice green (black also maybe) with decent lugs
Viscount I
Quinn Brothers made a few non mixte ladies which were light/nice to ride.
I hadn't seen the Dancelli, thanks for the link! I'm not sure it would suit though - the frame might be a bit racey for my missus, and the gipimme group with tubs wouldn't be suitable, so I'd be left with the problem of finding another frame to hang it on
For one reason or another, I'm not sure the project is going to go ahead though, not this year at least...