I sewed together the leather and the lining and proceeded to sort out the lacing in the back, inserting boning at the end piece and then eyelets for the lacing. Only to realize I'd made the whole thing a bit too wide; even lacing it all the way in, it looked and felt slack, so I had to do some cheating on the back panels to get rid of a couple of inches. That worked a treat!
Moving on from here, I started to work on the "winged" sweetheart neckline and straps. This was a fiddly process, but I got it right in the end, with the help of some pegs (!), and now, all that remains is to attach the two last bits on the straps, and then attach the latter in back!