I am thinking of flying to Kathmandu but with BA to Delhi, and then onward with Jet or Kingfisher a few hours later.

BA will be using terminal 3, and the KTM flight from terminal 2.

I have spoken to the Indian embassy in London and they say that a transit visa is not required if you are transferring from international to international. But they are unsure if you are transferring to a different terminal.
BA are similarly unsure, and the DEL airport website does not give information about t2 to t3.

Does anyone have any idea, what the situation is likely to be?