It's not clear to me what the best POD for this would be- perhaps Gandhi dying during one of his hunger strikes? Perhaps avoiding WW2, so that London remains intransigent in it's dealings with the INC?
It's my understanding that most of Britain's political establishment had more or less accepted eventual Indian independence as inevitable, so possibly they wouldn't even try to suppress the rebellion? However, if they did try, how would such a struggle play out? Should we expect that either the British occupiers or the Indian rebels would be quickly and decisively routed? Or would a long, drawn out struggle that turns into a meat-grinder for both sides would be more likely?