My only immediate reference are some 1/48 kits, Mk1, MkIX and MkXVI, and a Seafire XV, all of which have them marked, looks like they are held in place by screws or dzus fasteners.
According to Peter Arnold on Flypast's forum, the picture Dave has kindly posted actually shows parts of NH341 (presumably the cockpit section) and wreckage from another Spitfire (the confetti?) which is also poised to make a comeback as a two seater in due course.
You can never have too many airworthy Spitfires in my opinion!