I gave some information on this topic seven months ago here. To quote just my conclusion,

In sum, military technology on the battlefield was not critical to British success. Rather, the British subjugation of India was enabled first and foremost by the wider context of Mughal collapse. Within that context, the prime advantages of the British were their early control over Bengal, their unparalleled sea power (greatly facilitating both economic and military ascendancy), their national solidarity, and their institutional solidity. But, in the end, there was a great deal of luck.