Upvote:16
Since your flight left from a EU member state, regulation 261/2004 indeed applies to you. This regulation entitles you to compensation and assistance from the airline in case of a long delay/cancellation. Your flight was over 3500 km and went outside the EU, making it a type 3 flight. You can read on the link what exactly your rights were, but basically, the airline should have taken care of you, and you should be entitled to compensation. I'd submit a claim through Air India's customer service, or, if they won't react fast enough, through the UK's national enforcement body (contact info can be found in this document).