In the good ol’ days one could fly SQ between LHR and BOM. I think the closest thing that comes to it now is Kingfisher although I hear the inflight entertainment isn’t great, but the inflight service is. Kingfisher own Jet so, hopefully, the inflight service might be similar. However, be warned, Jet recently experienced disruptive industrial action and if you’re travelling with a child this could be a huge inconvenience if the pilots decide to go on another strike. You don’t want to be stranded at LHR or BOM/DEL with a child and in the event of a strike. You might want to check if Jet, should you decide to fly them, will re-book you on another airline or, alternatively, provide you with accommodation near the airport.