The british coaches cause clipping with all locos. I believe the problem is caused by the different coupler types, when switching to hook the bumpers expand but the colision model doesnt. take a look: Buckleeye before: Buckleeye after: Its only slightly clipping... Hook before: Hook after: you can see they are clipping in each other, not just the case with this loco (class 33), it happens to all of them.
This bug has been around forever, i don't see any fix forthcoming as they tend not to revisit older Dlc's.. shame though as it looks horrid.
what a shame, i mean you can see it in the steam pics of this DLC, at least they should reuse these locos on other routes but i guess that also gets down to us when there`ll ever be an editor