One of the best resources for getting into this period is Mike Kirby's The Campaigns In India During The Seven Years War.
If you have any interest at all in the period I recommend you get the book. There is information on uniforms, battles, army composition and figure availability (although the latter is now a bit out of date). The author's preference is for Volley & Bayonet as a rule set, but this doesn't detract from his suggestions for amendments/ modifications which apply equally to all rulesets. There are even some nice random event card suggestions.
The author has also viewed numerous British sources firsthand. The information presented seems accurate to me, more than can be said of a recent publication that I may review in the future.
I understand that the book was heavily edited before publication and segments not included. I think this shows in spots, and detracts slightly. Nonetheless, it is a very useful publication. If you are a gamer and only have one book on the period this is the one!
The book is available from On Military Matters, Caliver Books and Miniature Wargames.