Having looked under a few Disco's if you lift them then the axle is going to rotate as the arms are fixed rigidly to the axle so whatever springs you use to lift it the end result is the same with the axle not twisting but rotating so the spring platforms (on the front axle) will twist forward. Over a certain lift aren't you supposed to use caster correction arms to rotate the axle back to correct angle
Agreed the BP springs shouldn't have this issue with a gap between the spring and spring seat, have you thought about contacting BP direct, they do have a technical department in Caerphilly and I know one of the guys that works there if that helps