Many thanks.
I would suggest a steel or other metal box (a metal biscuit tin should be enough?), just to be safe. Belt and braces and all that.
This pretensioner is mechanical (rather than the electrical version MG Rover has). So this type has a spring and weight.
As I understand it, when high enough forces overcome the spring's force it releases the striker that then ignites the "charge", tightening the cable.
As the pretensioner is new and boxed, I believe it is "safe" from the factory. There is an internal locking pin to stop the striker from moving.
So I would just be sure to not get in any "wacky races" on the drive down.
