I have a WE 881 (Eotech 551 replica) I wouldn't recommend it, the reticule is blurry and reflects making two reticules appear (although this is apparently common in all cheap eotech replicas. also the elevation dial has stopped working so i cant properly zero it however this could just be with mine/the eotechs as they do a variety of other sights that seem popular such as aimpoint comp M4, aimpoint T1 micro, trijicon acogs etc.. Im suprised the hawke died on you as their rated for air rifles and shotguns.
UTG are supposed to be good in terms of bang for your buck and are popular with are American brothers on their ARs
I have been looking at this one recently:
http://www.military-outdoor.co.uk/products/utg-leapers-4-2-inch-ita-red-green-2-qd-mounts-dot-sight
just look around and check to make sure their "firearm rated" if they are, they should hold up on your gbbr