We’re traveling British Airways from Heathrow to Singapore. How early can I check bags in? Is there a bag drop?
It depends what class you're traveling in and what status you have. If you're in First or Business (which BA brands as Club World), or you have any status in BA Executive Club, you can drop your bags from 5am on the day of the flight. Otherwise, bag drop opens 3 hours before departure, or 5am, whichever is later.
BA also offers a bag collection service via a company called Airportr. If you use this service, you can book a collection slot online. They require that you are already checked in at the time your bags are collected, and online check in opens 24 hours before the flight.