I am going on the understanding that swapping back and forth won't cost me anything, will let you know when I get them changed, if there is any cost it won't be happening and I will be going to the motoring ombudsman.
You are correct regarding the incompetence, the original mail from MB said they only had issues sourcing 21 inch all weathers for the 43, they are the only ones they have been able to source 8 months on.
2017 GLC AMG43 premium plus, night pack, leather, intel lights, 360 camera, side steps. = sadly gone
Now GLE450 Premium plus, Selenite, Black/White Nappa leather, Tech plus pack, Driving assistance pack, Tow pack, Off road pack, 22 inch wheels.