I usually need the socket for the sat nav or phone charger so I decided to add more, I bought 4 12v in line sockets off ebay, then soldered them onto the wire, which is actually just 2 core white AC wire, then when i took apart the centre console to tighten up my handbrake I then had access to the power going to the existing cigar socket. I had 4 new sockets and my plan was to put one at the front and back of the two front seats, i used cable ties to hold them up onto the bottom of the seats then I threaded the wire from the sockets under the seat, through the carpet (leaving a bit of slack in the cable so moving the seat forward and backwards didn't break anything) and up in under the centre console and connected all up to the wires of the original socket. It was important to get the cable ties to hold the sockets tight under the seats otherwise they would rattle.
Below shows the Sockets located in the car:
And this one shows the phone charger which is connected to the back of the passenger seat socket:
Its a great job now because I can keep the phone charging away in the cup holder, and use the sat nav at the same time, and if any passengers need power its there. 4 additional power sockets may seem like too much but they are like cup holders the more the better. I have no worries about an overload because it can cope easily with things like a sat nav or phone charger, the only thing i would worry about is connecting one of them power inverters as they really should be connected direct to the battery. But overall these ones under the seat are good because they are hidden so don't look unsightly and they did not need drilling any holes which fixed sockets would need, and I did not find many places suitable for fixed sockets, and this way it cost less than £10 to do, its hard to find a fixed cigar socket for less than £5 never mind 4 and the wires needed.
