I've made this base now, and a couple of curries using it too. I'm afraid it's way off the mark, for me.
I made it exactly as Terry's recipe states, with no alterations, and with the Rajah Gold and all-purpose seasoning that he kindly sent me.
The fact that CK, CQ and others have said that it produces some of the best curries they've made can only show - I think - how different some of our individual goals in replicating BIR curries must be. Perhaps we're all searching for a different quality, influenced by our favourite restaurants, experiences, and even region of the country.
I now think it's entirely possible that if some of you tried a curry from my favourite local takeaway, you wouldn't like it at all.
But anyway, thanks again Terry for sharing the recipe and making the necessary spices available to us.