Hey Dryhorrors,
Before you lash out on a camping fridge/freezer, just do some shopping around as there are different physical sizes to fit when transporting to your hunting grounds. I have a 50L and it is too big to fit into my campertrailer (should of done the measurements before hand).
Also, before you go out for a few days, run the unit at home on 240v for at least 24hrs. Why, the start up current of your fridge when placed straight on the battery will place a drain on your battery before a recharge. This will maximise your battery AHs'.
Peter.