BA 'historic' use of Flaps 25 stemmed from operating 747-100s which tended to suffer from problems including sections detaching when selected. At one time, BA operated 80 747s with a mix of 200s and 400s. The significance of using Flaps 25 v. Flaps 30 was to save fuel and noise (R-R engines required 0.03 EPR less for Flaps 25).
Autobrakes 4 is common for wet runways with a certain SE Asian 747 operator and the difference between 3 and 4 is not that noticeable. I always preferred Flaps 30, full reverse and manual braking for a heavy (300t) freighter landing, especially during the summer in the Gulf area.
One point about the QANTAS accident, is that it was raining so hard that several operators (including BA) delayed departure. That might mean that the runway had a great deal more water on it than a 'wet' runway from ATC reports.It could also mean that the landing distance calculated by "Old Fella" if full reverse and Flaps 30 had been selected, is erroneous.