I posted this on another thread but thought it may be worthy of a thread of its own.
I indicate whether there is anyone to see me or not. If anyone sees my signal (pedestrian, driver in a parked car about to pull out, other motorist) then it has not been wasted. I no one sees it then it is like the tree that falls in the wood (If no one sees it, does it make a sound?). The instructor on my PCV trained advocated that, as did the driving instructor who carried out my assessment a few weeks back.
The only time I do not signal is when returning to my own lane after overtaking. Again something I was taught on my PCV training. The Highway Code says you drive on the left so there is no need to signal. It is a given. The only exception is, if you have a Beemer or the like, right up your chuff, then I signal, to put him off undertaking as I allow space in front of the vehicle I have just overtaken.