I spent the weekend giving this old Airfix Lysander kit a cockpit/interior. I shared a pic of the instruction sheet so you can see what was not there. I still have some stuff to add to the rear deck (including the gun). I didn't waste time on anything below the rim of the cockpit, as the canopy is so thick you won't really see details, but at least you'll get the idea of the structure inside. The last pic shows the fuel tank between the seats.
Some more work on the Lysander - reamed out and thinned the back side of the engine cowling, leaving the solid inside to mate with the fuselage. Drilled out the intake on the chin of the cowling; added push rods, intakes and other details to the engine; used a block of styrene to sculpt an appropriate exhaust and hollow it out.