Sorry you're not getting 'the taste' from your bases, Steve, but thanks for the Chettinad recipe. I came across another one here:
http://solaiachiskitchen.blogspot.co.uk/2008/03/chettinad-chicken-authentic-chettinad.html. They both sound delicious, so I think I'll cook one of each!
P.S. In the early days I found I was getting too hung up on bases, trying loads of different ones and generally overcomplicating things, and achieving nothing other than frustration. Remember that a BIR base gravy is just that - a base. In this case, a simple, lightly spiced onion and veg stew/soup. It's never going to give you that 'BIR taste' on it's own. On its own it will only be a simple, lightly spiced onion/veg stew/soup. Next time you order a takeaway ask for a portion of base gravy to take back home with you. I can guarantee that it will taste just like a simple, lightly spiced onion/veg stew/soup.
Yes, you have to cook it properly, and a well cooked base will produce a better end result, but once I accepted that the base was just a part of the formula, and that it's what comes after that created the 'BIR taste', it set me free.
'The taste' isn't down to any one thing, but a myriad of little things put together in the right way and with the right technique. Keep at it and then keep at it some more, and you WILL get there!