Yep Autosol
I had a seat that was looking pretty ropey but was structurally sound - it had a really ground in mucky "greyness" to it and little marks and even what looked like tiny white paint spots
I'd given it a good scrub in warm soapy water with a non scratch kitchen pad but it still wasn't shifting
Thinking about the mild abrassiveness of autosol and thinking about the very faintly textured surface of the seat I thought why not give it a go
Tried it out on the back corner which you can see in the first pic, and then went for it all over. Autosol applied in circles with the non scratch kitchen pad and then washed off with soapy water. It's not perfect but it never was to begin with and it's a sh!t load better. I reckon it just needs some plastic restorer (meguirs ?
) applied over it now to "lift" the finish on it and it's a decent survivor seat
Before (with test area in bottom left corner of pic) :
After autosol treatment: