Worth looking at the Engel range. Expensive but I think they're worth it. I use a 45 litre unit which can function as either a fridge or a freezer. Ruuns on 12v (properly - unlike thermo coolers) or 240v. Usually gets left in the back of my Discovery although could easily fit in a caravan or awning.
Importers are MPS trading I think - just look at www.englefridges.co.uk