Apparently the ARB bush isn't correct for my 05, but those are cheap anyway
I've just measured the poly ARB bush in an old bush housing, to see why they say they don't fit.
As it turns out, I'm pretty confident that the poly ARB will fit. It measures 20mm when pinched by the bush housing.
I also noticed that the bush has a built-in O rings on each side, presumably to help retain the silicone grease for lower maintenance. It's difficult to see in this picture, but it's there, and a good idea too.