Hi there - I have no anti mustafa feelings, at least not yet. That being said, I've gone there once only. Then again, I've caught the Northern line in the middle of rush hour when its 33 degrees out (never mind in), do that often enough and few things cease to worry you.
I did look for corn starch as well, but have not been able to find either. Perhaps the markets I was looking in were too small, however I'll pop along to Mustafa this weekend and see what I can find.
Thanks for the help. We're one step closer to chana masala and tarka daal.
Sarah