I received my replacement covers yesterday, all securely packaged up, I can't fault Sopers at all.
I was quite surprised to see that the covers come with new heated elements already fitted and what I presume is the occupancy sensor. Explains why they are not the cheapest things to replace I guess.
I'm not sure how you would get on if you had a retrim, I guess the retrimmer would have to carefully remove your existing heaters and sensor and stitch them in to the new leather/cushion.