Isn't there a discussion going on to stop the 15:00 rule once T5
This means that aircraft would land and take off both on 27L and 27R.
Of course, when winds are coming from the East, 09L would be used for landings and 09R for arrivals.
One small thing: in the early morning, the traffic is always divided between 27L and 27R for arrivals. As far as I remember, the same applies for 09L/09R in the early morning.
It will be a very long taxi for BA
when they'll have to go from T5
to 27L for take off!