Good evening shankari 1242, and welcome to the BA board. Someone ever so important will be along to welcome you shortly I expect but we are pleased to see you.
You need to give us some more information about class of travel and dates. You may also find flights by looking at the PHX to LHR and then LHR to DEL separately. I can for some random dates I tried, although there was not much.
There are experts on this sort of thing who can offer you advice when they read your post.
Award Nexus is an internet tool (app? I'm not sure) that many people use to help locate award flights. I've never used it so cannot say more.