On Sat, 10 Mar 2012 10:34:27 -0000
"Hugh - Was Invisible" wrote:

Not sure of safety of changing bulbs in permanently wired screw
lights because of the possible risk of the outer being live because
the neutral is switched.

All the recent ES lampholders I've seen have a non conducting thread
with a small brass side contact near the bottom of the thread . By the
time the cap becomes live it should be screwed in too far for your
fingers to reach it.

--
Mike Clarke