I found this elsewhere:
Land Rover springs & weights

This information supports what Evelyn has said with regards to the front springs being dedicated to a particular side of the vehicle.

The numbers alluded to also suggest that my r/h front spring is indeed fitted correctly.

The lack of a number on my passenger side spring leaves the door open to possibilities that perhaps an incorrect spring has been fitted, however I doubt it, as that would mean that the spring would be rated at greater than what I have on the drivers side. This is unlikely and I suppose it confirms that the front right spring has indeed sagged a bit.

Time to ponder the route from here.

Regards,
Ross.