This is probably not much help, but, looking at the shape, it looks like a piece of armour plate from the bulkhead, immediately behind the pilot's head, from a Hurricane. The 'slot' at the bottom would be where the 'Sutton' seat harness passed through. I'm not sure about this, but the shape at the top looks right, as well as the screw holes. Might have narrowed things down for you I hope?