<<I know it's a bit late, but I found out from PB that the most likely date for the change from 28s/10s to 27s/09s was the night of 2nd July 1987>>
I recall it well.. BAA had commissioned the heaviest moving equipment to move the runways round that few degrees but by about 3am they had to give up. Fortunately I was able to hastily get my Reliant Robin (it was HTF 443N Al) from the car park and that extra power enabled them to reposition the runways in time for the morning rush.
NURSE... the screens.. quick....