If I'm driving anywhere, I read a map a couple of times, memorise it and go there
Good luck trying to get across London using that method - unless you have a few years spare to do the Knowledge..
(And yes - my GPS recently took me on a jolly through South London instead of round the M25. Yes, there was traffic on the M25 but I'd rather be sitting on traffic there rather than trying to dodge insane cyclists and taxis in Greenwich.)
 Quite possibly operator error (although I'd deny that if pressed) - once you put in the destination it shows you potential routes and there is a vague possibility that I selected the wrong one. In my defense, I had just attended my mother's funeral..
 Which, as we civilised people from North London know, is a vast and wailing wilderness, full of subhuman denizens who grunt at eath other in a debased form of LondonSpeak.
 As always. And the extra two hours that it took me to get back out of London onto the M25 meant that we hit it at 16:30 rather than 14:30. On a Friday. Lucky us..