I live just outside Chobham and noticed a couple of months ago that MID departures from the 27s were passing about 3 or 4 miles west of me instead of overhead, then it reverted to passing overhead for a few weeks, however instead of being in a turn overhead, they were passing in a straight climb. Late at night, the noise they generate is louder as if they are being held down for some reason.
For the the last week, they've been back on the route which passes to the west of Chobham.