Well, I've ordered one, it should arrive by Tuesday so I'll use it to calibrate my existing wrenches and report my findings back.
I have two Norbar twist end cap, (One small, one large) and a Lidl special large one I bought last year and which I leave set at 75Nm/55lbf for wheel nuts.
We'll see if any of them need tweaking to bring up to spec.
After this I will of course be offering torque wrench recalibration services for a modest charge.. 😬