Thats the sort of thing I am looking at, I have been looking at a few square ones for a few quid less.
The intention is that I leave my cig lighter free in the front for my gadgets, and then plug the kids into the boot, but I would want to be able to switch it off from the cabin if at all possible, I just dont know if it is!
You just need a normal inverter similar to what people have in caravans etc. Get a decent one and it will wire directly onto the cars battery. My company owns a few Discovery's which we require inverters into not only run TV screens but also run items such as stabilised cameras, CCU's, PSU's, Chargers, Talkback units etc. (They are Discovery's for TV Use we also do the same with some ford transits) Really quick and easy to install, The only problem comes with hiding it. Might be able to fit one under one of the front seats, if not put it in the boot and just run a normal 240V cable from it with a 3 or 4 gang socket on it (or less if required)
The only thing you might need to do is occasionally top the cars battery up if stuff is going to be often used when the car is turned off etc. basically make sure you always have either a set of jump leads of a trickle charger on hand for just incase.
Take a look at some caravan sights etc and you should be able to see what they do.
what about something like and you wont need to bother with 240v at all, just plug it into the cigarette lighter
admitedly thats a refurbished one, but im sure theres plenty of new ones available, which will be alot less faff and wiring.