No idea so I'm guessing it was the Merlin because I don't know how to tell the difference in the engine noise. All I do know is that is sounded superb.
The Filton based Spitfire is a PRXIX - with a Griffon.
I've sat in that one, we used it once for a photo-shoot. IIRC it's the oldest airworthy unrestored Spitfire to have seen active service, or something like that. It certainly has a lovely, unrestored patina.