Snooky:
It is strange that BA should not accept the promulgated runway without good reason, I agree and I would like to know if there was.
Incidentally, the IRVR at 09L touchdown was worse (as it nearly always is due the resevoirs) than 27L and that is why, having landed this a/c on 09L, ATC changed back to Westerlies. Also, as this aircraft is a LAM arrival, 09L added some 30 miles to his intermediate approach.
Your point about the lower limit runway is valid but we don't get involved in the noise issue, except for attempting CDAs (near impossible if you want a good landing rate on both runways!).
The "correct" landing runway is predetermined according to a strict rotation. Towards the end of the night shift Tower tell us which is the correct landing runway and, wx permitting, we use it. (The use of the other runway for landing is dependant on us having 10 minutes delay between 06:00 and 06:30 and 5 minutes delay between 06:30 and 07:00.)
Point 4