The British came to India to harvest rubber and opium and exporting it to China for money. They also built railways and dominated it's cotton industry.
A link to an article which provides a background to British involvement in India:
http://www.bbc.co.uk/history/british/empire_seapower/east_india_01.shtml
http://www.bbc.co.uk/history/british/empire_seapower/east_india_01.shtml