I'm sure we all understand that Paulilf's posts are arriving a long time after he is sending them (presumably due to moderation) which makes them read a little oddly.
1. There is very little holding an ejection seat into an aircraft (which another tragedy illustrated rather too well) so it is unlikely to remain in place in such an impact.
2. Tornado has a command eject system, if the nav's seat has not been fired then neither has the pilot's.
3. This is not the only case of an ejected casualty not being recovered from the North Sea, there are many options for entanglement on the sea bed and strong currents.
4. Jamming pods, 'exotic' construction materials, practice bombs, gaseous light sources, unfired live seats, an aircraft which (at that date) neither air- nor groundcrew really understood, previous cases of hepatitis from recovering casualties. The MOD advice would be very cautious, and, to someone not familiar with officialdom, its tone might be misinterpreted.
5. Maybe the MOD had a contract with a fishing company for search work which would be under MOD control with appropriate personnel on board.