Managed to source a set of sedan sports seats which should arrive in a few days.
They're a bit worse for wear, and will certainly require recovering.
I've read a few good reviews about the E30 replacement covers sold by LSeat.com, and the price was far cheaper than paying for someone local to do a custom job. https://www.lseat.com/products/1984-1991-bmw-e30-sport-325-318-custom-real-leather-seat-covers-front.html
I decided to go with a nice dark red leather with diamond stitching for the fronts. Sadly (but not unsurprisingly), they don't have any options for the split rear seats of the E30 Touring.
So for now, I'll just do the fronts. If I'm happy with how the front seats turn out, I'll order some more leather in the same color, and take the rear seats to a local upholster to complete the look.
I've got this coming week off, so I'm going to try get as many of the remaining jobs sorted as I can.
Looking forward to making some more progress.