I really rate the natco grail base, I dont use the onion soap thing though just the base.
I have just finished using up all of my first batch of base and I can honestly say every curry I cooked from it was superb, way better than any other curry I have cooked, and smelt and tasted like it was from a BIR.
I wont be using any other base again (unless a new one pops up which Ill try once), it really is that good!
Next weekend I will be cooking my second lot of base, this will tell me if my first base was just a fluke.
I think the difference in this base is that the onions are fried (I sweated mine for at least 30 minutes covered) and the huge quanity of garlic (1.5 large bulbs for 7 individual portions)