I heard these about 2010 on BBC Radio 4. It seemed to have been written recently.
The protagonist is a lady going for a job interview at the place, several buildings on one site, where the clones are raised.
The clones walk around wearing overalls. They are taught a very limited vocabulary and to follow simple instructions. The people running the place still claim they are not intelligent.
It is really haunting. One of the clones Carter 5 has his eyes removed when the rich young man he is cloned from damages his. The clone in kept sedated thereafter in 'high dependency '. Another clone sees him, goes back to the barracks and say to his peers "Carter 5 no eyes."
At one point one of the clones is asking too many questions and they decide to kill him. His identical clone brother swaps identification bracelets with him, sacrificing himself to save his brothers life.
There were several 30 minute installments.