Re: switch off your Wi-Fi...
"For the privacy-conscious Londoner, the easiest way to not be tracked is to switch off your Wi-Fi."
And switch off Bluetooth while you're at it as that can be tracked too, although the shorter range makes it a bit more difficult. Switch them on when you need them, and leave them off at other times to save battery as well as avoid tracking. It's not just Tube stations, shopping centres are another that like to
track "Footfall" offer free Wifi and ping you with targeted advertising into the bargain.
I use Wifi at home then turn off Wifi and stick to cellular when out and about then it's only your mobile operator and the Gubbermint that's tracking you.