I need to find a definitive list of US and UK index constituents. I'm currently monitoring S&P100, S&P500, DJIA, FTSE100, FTSE350 etc. and curating the list manually, which is causing problems. M&A, delisting, renames events are causing my code to go astray.
I've had a look at Intrinio and Quandl and cannot see an obvious candidate. A HTTP REST API would be ideal but flexible enough to implement most things.