Got the jack clamping arrangement sorted today. Basically just drilled a hole in the spare wheel carrier bit and put a riv-nut into it for an M10 bolt and bolted on the clamping part I made last week, job done, it really seems to hold it tight. Of cause I’ll have to put that to the test at some point.
The draw back to this arrangement is now I need to carry a 14 mm spanner to release the bolt at the bottom each time. I have not fixed the wooden bits in place either, I am hoping that they’ll remain where they are just by friction or magic.
A bit of car door seal on the clamp part should make it grip well and also make it salient by comparison with the noise that the land rover generates.