Without checking full facts, there were a number of successful abandonments, including from Mk 1.
Five-out over Valley was a Mk 1. It also had a number of secret documents and a couple of filing cabinets on board too - well that it what was said to account for a number of missing inventory items.
Then another 5 in the east coast crash where they again had time to prepare.
One fatal, but ejectable, was the control restriction, due to a bombbay overheat, at Cottesmore. The aircraft was above normal landing weight so, in accordance with current thinking and advice from the tower, the captain burnt down to below 140 000 lbs. As the magic weight approached the control column defelection became excessive and the aircraft rolled in. The coplit banged out to tell the tale and the captain remained beyond the seat limits. He banged out and was arrested by some power cables. The rest was a hole in the ground.
The sequel to the east coast crash, same pilot, was a rather firm landing at Malta and a take-off to sort out the problem. On the recovery teh aircraft became uncontrollable and the pilots both departed. A couple of friends of mine also 'bought the farm.'
Several other crashes were controlled flight into the ground so the bang seats would not work.
We once tried a low-level simulated abandoment after a massive bird strike with undercarriage up. Impressive, we made 1 500 feet on flight idle before the speed decayed and we started a gentle descent. The real bastard was the loss of control.