Yes, thats what you are after (the socket with the little lift up cover buy the footrest). If your happy to wire it up yourself, then the din plugs on their own are cheap. It is a very straight forward job. For chargers such as optimate etc, I just fitted a din plug and away you go. The ready made adapters listed on ebay allow you to keep the standard cigar lighter socket which could be useful if you intend charging your phone etc in the car as well.
Do a few searches on here and you will see that you can easily put an extra socket in up buy the clocks, which is proberbly a better place to fit it.
==yes, you can charge through this socket but use an optimate (trickle) type charger.