Nothing interesting about an overnight in Delhi airport! A visa for UK nationals is about £100 pp so not worth getting for a single night out of the airport.
The flight is to / from Aus so we splash out a little for the opportunity to sleep properly on the flight and make the most of our time in Aus. We've done this trip before in economy and spent 2 days in a zombie like state.... after a 13h flight from Singapore.
AI are by far the cheapest (J) at the moment so the very long return journey (40h including the overnight) is worth it for us....
Didn't expect AI to stump up for the hotel - I was about to book it!