OK, based on the advice I got, I took the said bathroom scales and placed on level ground.
A flat block of timber and a car stand, lower jockey wheel and swing up, to prove I didn't cheat.
One will note, I took the weight as far forward as I could by turning the tregg on its side.
This is the weight reading including the timber and the car stand @ 70.9kg.
There was still a bit of gear in the front box as well as stuff in the camper itself. By cheating, I reckon I could've got this down to around 65kg and by the same token, poor loading could see you go past your 75kg limit, but you'll work all that out when you get the camper home.
Yeah yeah, the scales could do with a clean.