No, the southern airports don't change at the same time, the wind could be significantly different at each, and besides Stansted have a NE/SW runway whereas the rest of us (mainly) have E/W.
At Luton we agree with the Intermediate Director (at TC) after which inbound we are going to switch, keep the outbounds going to the old runway until that time, then make sure we have the outbounds going to the other end afterwards.
Tell all the people radar707 mentions and some besides, throw all the switches, get a radar release on the first departure off the new end, and Bob's your uncle!
VA