[Ian_T_H]

Hello Matteo, lots of interesting bits of Seafire? there! On the other forum I said Seafires had .5 guns which was a mistake, they do have .303 guns for the cases you found. Also the R3002 is part of the Identification Friend Or Foe (IFF) controls. Lots of types had these.
Photo 1 is armour plate from the front of the pilot's seat, under his legs.
Photo 2, you are correct, a lifting point from the front of a Merlin engine.
3, top right is a catch to hold the seat in position, bottom left looks like the recoil buffer from the back of a .303 gun. Bottom right is the end of the seat adjusting handle.
9 is the fuel filler cap from in front of the windscreen.
10 Brass part is the slider for the canopy. It fits in the long slot you found at the other Spitfire, try it! Stainless stell part is the catch which holds the cockpit canopy in the 'back' position. This is different to ones I've seen on Spitfires so could be a clue
11. Topright is the 'flick' bit of a cockpit switch. None of the other bits are parachute.
15 is part of an oxygen gauge from an early Spitfire/Seafire.

I will try and find photos. All the best, Ian.