Teach English-style curricula in all the schools, with English lessons, studying famous English authors, etc. Incentivise assimilation by giving Anglicised Indians prestigious government jobs. Give the vote and other political privileges to Anglicised Indians. Establish veteran colonies to help spread English culture. Give civil privileges to towns that establish British-style civic institutions. Remain in control for five hundred years or more to make sure the reforms can properly bed down. Plus, they wouldn't need to "wipe out" Indian culture, just to bring over enough of the middle and upper classes, who'd be the ones leading any putative independence movement. It doesn't really matter what the peasants think, as long as the middle and above classes support the British India isn't going to cause any trouble.