We have flown London to India several times, we have done both direct and indirect flights.
Where do you plan to fly into, that will affect your price?
We have flown twice with Etihad via Abu Dhabi (short change about 1hr 30, get off plane, go through security again and board another plane, luggage checked through as booked on one ticket), flight was fine and it tends to be cheaper doing it this way we have found, but is obviously longer and you have increased risk now in Covid world of having various restrictions imposed based on where you are flying from/through so I would probably go direct for any upcoming bookings just in case.
We have flown Air India direct and the food was not great, but for a low price the flight is fine. They have had widely publicised financial difficulties pre-Covid, so I would ensure your insurance is good/book on credit card.
My boyfriend has flown KLM, Air France, Lufthansa, Virgin and BA to India and would recommend either KLM or Lufthansa but both are indirect via either Amsterdam or Munich.
Be aware that many airlines use older planes on less profitable routes.
Given India’s current Covid numbers and inability to do another full lockdown make sure you have adequate insurance which covers Covid disruption before spending any money - I believe Allianz and Trailfinders are currently offering this on post-Covid bookings.
Your tour may organise it for you, but the e-visa is super handy and easy to do (make sure to print it).