We had the 4 seats and carpets replaced in our Archer by an automotive restorer, with our licensed engineer overseeing and approving the work. I chose leather with a cloth insert for extra breathability (I do 300+ hours a year in the right seat!)
We also had the cushion material replaced as the original was badly sagged. The whole cost us circa £1,000. We didn't have the side walls done at that stage as we're having a paint-off respray next year with new transparencies so will have them done then.
My advice is to find a good automotive restorer locally and get your licensed engineer on side.
I've seen some horrendously bad jobs done up-country by people purporting to specialise in light aircraft.
TOO