Does “barn find” really make a difference?
Depends how devote a follower the buyer is…
I reckon if it was a Mk1/2 Escourt you’d get more money with pics of it looking original and dusty in a barn/garage/shed than if it was the same car all cleaned up, but with an MX-5 I don’t know.
Some people do get all giddy at the idea of something that’s like a time warp, left somewhere dry and dusty in a ‘barn’ like finding a Monet hidden in a barn from the Nazis or something, but the more pragmatic amongst us just see a car that someone stopped using for a reason and forgot about it.
As OP was ready to let the scrappy have it, I’d go down that route – leave or make it dusty, take pics with as-is and list as “rare special edition MX-5 barn find” for a laugh, worst case the MX-5 community will all be talking about you and you’ll gain more interest.