Thanks for the responses both. I'll look into those. No the Landy is not sagging at all and manages well with loads, but it's quite possible the suspension has barely been looked at since new.

Our 20 odd year old Defender can sway from side to side when overtaking lorries and the like on the motorway when fully laden on the roof. We're about to put the new roof tent on there and I wonder if fellow owners had any recommendations as to whether to firm up the suspension, the cost, and...