Britpart yellow springs are not handed, I'm not sure any after market ones are, I know Bearmach blues are not handed or Old Man Emu, I spent so much time on my last Defender as the lean on the near side was 25mm, changing between OME, standard, BP yellow, changed all the king pin bearings, still it leaned and eventually ended up with genuine LR HD front springs where the off side spring is roughly 15-20mm longer and it levelled it up and did not lose much of the two inch lift anyway. Odd thing is some Land Rovers are not affected by Landy lean.
I've just fitted LR HD fronts to my 110 with a winch bumper steering guard etc measuring from the top of the tire to the centre of the arch spat, the off side is nearly 6 inches and the near side is 5.5 inches, which is barely noticeable and will level out eventually.