I think I am going buy these boots, but like some of the others, I don't own any Wescos so really hard to guess sizing.
I am a 10-10.5D tweener in US sizing on a brannock.
I wear a USA 9.5D in all my RW boots including 877, Iron Ranger, Beckman, classic round toe
I wear a UK 9D in Tricker's stow boots (these are reputed to run true to size)
I wear a UK 8.5D in Tricker's bourton (these are reputed to run slightly big)
I wear a USA size 10D in Oakstreet Bootmakers trench boots (these are reputed to run true to size)
I wear a USA 10D in most running/tennis shoes, but once in a while I require a 10.5D
By reading this thread it sounds like folks would recommend a USA 9.5E in the Wesco boot. Please let me know your thoughts while I dream about these boots.