Did this job over the weekend myself, decided I may as well take a few pics along the way.
Items required:
Drill
drill bit and holesaw or cone shaped bit
spade cobnnectors
insulating tape
cigarette lighter socket (I used one from an FTO)
screwdriver
small flat file
I did this on the Avensis, but everything applies to the FTO too.
Drilling pilot hole, first make sure there is enough clearance behind the dash to fit the socket.
Used a cone shaped bit to get the correct hole size, there is a notch on the socket that stops it turning, I filed a corresponding slot into the dash.
Next I tapped into the + wire going to the original cig lighter (this is in the centre of the socket, earth is on the outside), soldered the joint then insulated
For the earth wire, I used the casing of the stereo as an earthing point.
I used spade connectors to connect the wiring to the new socket
The cig lighter socket has a large brass nut at the back. this holds the socket tight against the dash.
20 minute job, and so handy for charging phone and satnav at the same time.
Obviously you won't be using the extra socket for lighting 2 cigarettes at a time. you don't wanna overload the wiring now.