Just like to raise the point I have mentioned before. There is, at least in my mind, a difference between a coolbox and a fridge. Most coolboxes are basically normal insulated boxes with a 12v fan motor that will drop the temperature to about 18-20 degrees C below ambient. This means if you are the Scottish Hioghlands and it is the usul 12 degrees outside, the thing will get very cold indeed. If you are in the south of France in a heatwave and it is approaching 40 degrees then it will not work too well. They also usually come with a proviso that they should not be run continously, even with teh 240v transformer.
The fridge on the other hand will also suffer in the south of France, but not nearly as much, but tends to be much heavier due to the mechanism, as it runs on 12/240 and gas. Most 3 way box fridges come in around 16 kg empty.
I had a 3 way box fridge but due to the weight tried a cooler. It worked as well as it could be expected, but not what I realy wanted in the deep south. However, it was great for collecting frozen food from the supermarket and keeping it frozen until one was back at the van and could transfer the goodies to the freezer part of the van fridge. Also good for cooling beer and wine, but I would not risk uncooked food for too long, unless of course one was in the aforementioned Scottish Highlands.