I don't know what you're doing differently Phil. I'm not getting any oil separation out of Syed's base, even after extended cooking. Maybe something to do with your preservation process as mine is in the fridge.
I had oil come out of the Chicken Bhuna/Rogon during the reduction stage, and I did remove some, but I put that down as being my own fault due to not actually measuring the oil into the pan and I know I put in excess ghee.