Hi Una --
First, as one abdominal-zone-pain, post-surgery woman to another, I have some advice:
start preparing mentally for needing the non-binding clothes til TBD and closet edit (remove / put in holding zone) and shop with that in mind. Whatever's uncomfortable now needs to go out of your immediate vicinity.
I had less removed than you and still it took several months for swelling to go down. That's just nature at work, really. One annoying thing is that I wore loose-at-waist pants back to work but when I sat the lower waistband hit in ways that hurt (grrr). So really knit skirts and dresses were my saviors -- despite being sick of them from so many years of pre-op wear!
Also, don't know if your op is minimally invasive (mine was) but scar tissue forms for about a year after and you may find you have pressure points that don't take to the barest restriction. I know you'll be feeling TONS better after surgery, but I'd say "shop/test run, shop/test run" for a good long time vs buying in bulk!
I'm a year-plus out and had pelvic floor PT (RECOMMEND!! start looking for a good one now!) as soon as I was cleared which helped with lots, esp adhesions, but had to go back this winter to let her have a crack at me. My spring jeans shopping was due in part to my old styles technically fitting fine but just hitting that scar tissue (again, grrrr).
Obviously YMMV with this! I will say most jeans now feel like jeggings so that's a plus hahaha -- I think I can stretch the waistband of my new ones by about 3 inches.
So: novel but I think you really have to start thinking about buying what you like for your current shape and sensibilities, knowing that this is a journey not an event.
Best wishes for getting things scheduled and moving forward!