Cheersthe bantam cockerel wouldn't be stressed at all. He would mate with the large fowl hens. They would also be able to get through the large holes in the fence. Just out of interest why would you keep the large fowl in the run and let the bantams out? Just wondering as I can't see why.
I don't know of any breeders in Kent who rear the way I do I'm afraid. You would have to phone some and ask them.
Having kept bantams before I found them a lot less destructive in the garden than the larger birds.The wyandotte colouring is so gorgeous it seems a shame not to be able to see them from the window (I know that's a terrible reason as I love my larger birds, but my husband also loves his borders!) My larger birds do come out freeranging quite frequently, more so in the summer when the ground is drier and they are less inclined to trash things. Maybe I was lucky in the past or unlucky now and some hens are more destructive than others.