Maybe a mod could move this to the how to section.
Fitting a 12v socket is relatively straightforward. It took me about an hour but that was being very careful removing panels.
If you look at the Volvo accessories website it list the part number 31435603 for the xc60,v40,v60 and some others. This kit contains a lots of bits that you do not need. It's only apx £37 but you throw most of it away, which seems a bit of a waste. All you need for the xc60 is the socket 31324708 and retaining collar 30653376 nothing else. The wiring is there already. You don't even need a fuse.
Tools wise you will need a very sharp knife, an 8mm and a 10mm socket set.
It fits just forward of the light bulb cover on the drivers side. The wiring is folded back on itself at the base on the panel on the drivers side. It is quite a long cable and just plugs into the back of the socket.
It would probably be possible to do it without removing any panels but it's easy enough to remove them.
This is a link showing you how to remove the side panel in the boot. Note it shows the opposite side that you need to remove but the principle is the same.
http://accessories.volvocars.com/en-...ll/XC60%202014
This shows you the back of the panel on a v40 which merely shows you how to cut the hole and mount the socket.
http://accessories.volvocars.com/en-...-470576-3/2013
That's it. Remove panel, cut hole, inset socket, attach plug. Reassemble. Done.