Nice, comprehensive update Paul. And just to add that my car has ALWAYS had a shock-to-header distance issue (but only one one side if you please), which was highlighted initially when fitting my Spax Adjustables, as the spring is longer and brings the bottom coils and adjuster into close proximity to the header.
Fitting my Empire Kit has not changed this whatsoever, ie: it is NOT the cause in my case at least. The 'fix' is to crank up the ride height just a touch, until clearance looks reasonable again. For what it's worth, I am now back to the 15cm height from very front of the 'tub' (measured each side from behind the wheel, under the rear wishbone mounts) to the ground. I tried it as low as 13.5cm at one point, but that was never going to give a workable clearance, so I am back up to stock ride-height I suspect. No discernible difference to me in handling over that 15mm or so change.
For me however, it's not just the lack of bumpsteer I notice, but the vast improvement in steering 'clarity' and delicacy that makes the Empire Kit stand out.