QR and GF are other airlines that serve LON-SIN via Doha, Qatar or Dubai which have decent fare and a good service. Yes - all stops are in the middle East.

I would say in terms of a decent stop-over, Dubai would be the best bet.

The other alternative is a long routing via Johannesburg, South Africa which would not really work for you as it involved 2 long flights.

Bombay is the alternative to Delhi but BOM is far more chaotic than DEL for international arrivals and departures. It is also a long drive into town given the traffic.