Originally Posted by corporate-wage-slave

Welcome to the BA forum SB15, welcome also to Flyertalk, I hope we will see more of you.

Yes, anyone with lounge access can drop their bags off at any time on the day of travel. I thought it was 05:00 hrs, but I tend to do my best never to be in LHR at that hour. You may be able to do it the night before (16:00hrs to 21:00 hrs) though strictly speaking this is for morning flights the next day, not those in the afternoon.