A few points to consider:
1. If an aircraft was designed to have an ejector seat, the canopy opening mechanism and/or the space available once it is open may not be suitable for a bail-out with a manually opened parachute. The Jet Provost Mk 3 & 4 has an entirely different canopy to the Mk 5/5A. I believe that there are many Mk 3s and 4s operated with inhibited seats but with the option of a manual bail out. However, the Mk 5 canopy set-up is not conducive to a manual bail-out and I would not fly one without live seats (although I believe that they do in the USA).
2. If you do not have live seats and you have an engine failure below a sensible bail-out height (around 1500 ft), you are committed to a forced landing. Do you want to try to land a heavy aircraft with a high glide threshold speed in a field? The training for all ejection seat aircraft is that you do not forced-land off a runway; you eject (even in the Tucano which is a similar AUW and threshold speed to many warbirds).
3. The big benefit of a military background when flying these aircraft is that you know when to activate the maxim "Eject in time". In the Hunter accident at Dunsfold the pilot did not.
4. If anyone is going to quote statistics on successful ejections, please qualify these with whether or not they were made inside the safe ejection envelope. It is important that we differentiate between pilot decision making and seat reliability.