I just thought I'd let you know that I made your bhuna pretty much to your specification, but without the Chalice oil and I thought it was quite excellent.
The main difference was that I pre-cooked my lamb in some of the marinade with added water and simmered it for about an hour and a half until just tender. I then added it along with your instructions. For me personally, I'd make a few tweaks for my own taste, but I'd highly recommend this as being a very worthwhile dish to try as per your instructions.
Well done for coming up with such a great dish.
Good Karma