All done and dusted!
The leg thingies (this is the technical term) are white bodycon. I cut lengths long and wide enough for each leg, and then used a lot of trial and error to position the rings and make the legs fitted. The rings are attached by a strip of fabric on each side. I then folded the excess fabric around my feet/ankles to create a sort of stirrup strap so they don't ride up.
Next, I cut out the shape for the things at the top of each leg in bodycon, so I had double for each leg. I sewed them together and turned them inside out. I then side the same but slightly smaller in black cotton and attached it to the white part, and sewed a gold button on each. Using more small strips of white bodycon, I attached them to gold rings, and then attached them to the top of each leg thingy.
The belt was a similar process. I first of all measured out and pinned a doubled-over strip of bodycon but didn't cut it out. Next, I positioned a diamond shaped paper pattern on each side to create the suspenders. With these in place, I cut the whole shape out. This way, I didn't have any visible seams. To reinforce the suspenders, I cut out another diamond for each side and sewed them to the attached ones before turning them inside out. I then rolled the belt part over and folded the edges in, so the seam was on the underneath edge.
For the black part, I pinned the whole bodycon belt/suspender combo to black cotton and cut around it. I unpinned it and then carefully folded over all the edges of the black piece and pinned it in place (so it was smaller than the white piece), before stitching it down. To finish off, I cut smaller diamonds out of white bodycon and sewed them to each suspender.
Before attaching this to the leg thingies, I carefully folded up one side of the belt, and slid a round buckle (with the centre pin removed) into the centre of the belt.
The last task was to attach the suspenders to the rings on the leg thingies, which I did with more strips of bodycon.
This was a very awkward explanation of how I did things... at some point I will take a photo of the whole ensemble!