At the risk of sounding totally boring, what oil do BIRs use?
Oil, it seems to me, is becoming (has become) prohibitively expensive (for whatever reason).
It also seems to me that, like many other things, the debate on "which oil is healthiest for you?" (read "least unhealthy") goes around and around.
It also seems to me that things like rice bran oil and peanut oil are very prohibitively expensive (at least twice as much as simple vegetable oil).
So, why not stick to what BIRs generally use (i.e. simple vegetable oil or, for the posh and health conscious ones, sunflower oil)?....if you wish to reproduce their results...health risks and all?
It seems to me that these sorts of changes are amongst the very reasons why BIR curries are apparently very different from (and not as good as) those of yesteryear.