We used one of the £30 12v cool boxes from Wollies last year, woked remarably well considering it was in the back of the MGF next to the engine! we did give it a helping hand by freezing everything we could beforehand, bottles of mineral water in the bottom, curry, bacon etc then put the beer and eggs butter etc on top. the only downside was not being able to run it for to long without the engine running. This year we are taking a 12v power pack (£30 from most places) to run it in the tent ,which we will charge from the car when out and about along side the cool box. Beers not Ice cold but not warm! and best solution within the spce constraint of the MG and total cost of £60.