I concur with Yellow Sun.
When a Mk2 folded up on the ground the canopy was jettisoned and the nav plotter exited through the bang seats trampling the copilots hand as he switched off the fuel pumps. In that instance the seats were live.
I can't recall where the seat pins were stowed although I routinely fitted the drogue chute pins. I recall one instance whe I fumbled a pin and it ended up in the guest plotter's nav bad. He refused to look for it and I only found it a week later after an illicit search.
The canopy pins however were a 2-way type. Pre-flight one pin was removed from the jettison gun and its mate, a pip-pin, was fitted in a guilotine type lever. The gun would fire and a lever would act against the pin pin.
On one flight I lived the canopy, the crew-chief then came up unnoticed and unthinkingly reversed the pins thus safing the canopy before flight.