Thanks for the info guys, much appreciated, and yeah. . . buying from "Really bad Design", what was I thinking!
Still can't pinpoint which part is out of whack though, going by the different measurements it could be the rack or the x-member.
The rack's the easy one to modify though, so I might as well just cut off the bush locating bracket & weld it back on in the right place, it's crooked as it is anyway.
Even the large bush doesn't fit properly.
It's 6mm too big across the bottom so I can't see how it's going to grip the rack tightly.
If I cut the bush into two pieces (not ideal, but it's workable) & remove 6mm from the bottom section so it fits, then the clamp won't grip the bush as the clamp is designed for the original bush size?
Or am I missing something there?

Surely that can't be right?
The rack mount measures 39mm at it's widest point & the bush is 45mm across the bottom.
The bushes came with the rack as did the clamps to fit them. The clamps were so far out that they went straight in the bin!