The effect is VERY slight but regular (approx 40 times per minute). It
is something I am aware of from time to time (so who is to say whether
it is intermitted or I just don't notice it). As i said, the effect is
very slight and it applies to lightling plugged into the mains sockets
as well as ceiling lights.
Stephen

Try taking a portable radio and tune it OFF station so you get a lot of
hiss then take it near to your mains inlet to the house. If it gets
worse the closer you get then call the Lekky Board.

Chris.