The daily checks for the 319/320/321 etc are carried out either last thing at night or first thing in the morning but they do get daily checks and that includes strobe lights. The 747 and 777's get their daily checks when they are at LHR, given the schedules this often happens during the daytime when passengers can see this happening. T5B is essentially used for LH ops and so that is where the 747s and 777s lurk.