Irish,
leather, vinyl, or fabric is the important question here.
If the original Cessna material was replaced with leather without changing anything else about the seat (foam), you might have a chance of making this work for the inspector. I've never heard of leather which does not pass the burn standards. It's worth the discussion with him.
The burn standards which are being called up are specific to aircraft, and based upon sucessful testing. Many fabrics (wool in particular) pass, and special treatments are sometimes used to make the fabric meet the standard, but this is not a well liked method, as the properties of the treatment are known to deteriorate over time, and the effect is lost. The test consists of burning (under very controlled conditions - by an accredited lab) three sapmles of the material, whose size is generally 3" by 12", though there can be some give on the size. The test in Canada costs about $400, and is pass or fail (you pay either way)
If the seats are vinyl, it might be possible to read manufacturer's information from the inside of the vinyl, it's often printed there. With a photo of that information, it might be possible to determine what the product is, and get the certification for that material from the manufacturer.
If you have fabric seats (or vinyl with no ID), it might be possible trim enough fron under the seats to get test samples, and do the burn test. If the inspector is being sticky, it's probably your only solution. If this is not an easy do, it'll be cheaper to have the seats redone with certified material than fight it.
PM me if you can't find a solution...
Pilot DAR