I made this last night using chicken in place of Lamb (bloody Iceland shut early - you get a good size pack of fresh lamb rump for 3.50 - I highly recommend it)
Anyway, the result was excellent. This is one recipe I feel really achieves 100 percent BIR quality results. The cumin and coriander as the spices work perfectly with this dish. My only tip would be to add plenty oil, as all those onions and peppers soak it up quite a bit.
I feel I'm getting there now, with my Bhuna and Korma (Georges) as good as I feel they are likely to be (in my opinion as good as a good BIR version). However the toughest nuts to crack are standard curry, Madras and Vindaloo. I still think most good BIRs attempts are better than mine... That said, I feel I am developing a nice little menu of dishes that are top notch.