May I comment on this, since I have had mady the C2G gravy?
Using his recipe, you end up with a pressure-cooker amount of base, after it has been blitzed. Yes, the pan was piled high to start with, but I was able to push it all down (rightly or wrongly) after a while and put a lid on it. He then said to add the same amount of water. So that gave me two pressure-cooker amounts of liquid. I made up his spice mix and divided it between these two. I got the consistency I saw in his videos, with a lot more blitzing.
To me, it tastes like very mildly spiced onion soup, with hardly any heat. It has a pleasant aftertaste, but no harsh notes. I have made two batches - for the first I didn't cook the onions for long enough, so it wasn't as sweet as the second, where I did.
I made his Bhuna last night for the family, which has no extra chilli powder. It does use his spice mix, for which I used medium Raja curry powder. That gave it enough of a kick, and to us it did taste very much like the sort of thing you would get in a BIR.
Julian says that his chef's spoon = two tablespoons, so I use that as my measure.
Only thing is the huge amount of base that you are left with. I'm going to make a large batch of his madras, without adding any meat, and give that to my son and his pals in Glasgow. I'll be interested to get their opinions.
BTW I did add a wee bit of fenugreek to the base, in the light of intelligence purloined from this site!