Hi Anish, I've decided that I'd just stick with economy as the seats are wide-open and I'm likely to get the whole block of three seats by myself, where as business class seems more packed.

Otherwise, I would asked at the airport ticketing office at Delhi Airport (apparently there are two at the either end of the terminal near visitor's waiting room), but not at the check-in counter as that'll likely to upgrade based on GUU.

Thanks for all the suggestions!