We do that too when going to France - but with frozen litre cartons of orange juice, which pack nicely on to the shelves of the fridge. We also freeze a few small cartons and they pack in any free spaces.
We also take a small coolbag inside a larger cool bag - and pack two frozen meals in it, along with anything else which want to keep very cold and some more frozen packs of orange jice. The first night on site in France(24 - 26 hours after we set off) we take out the top meal, and it's usually just defrosted enough to eat. The second night we take out the second meal - makes it so easy arriving on site, with a ready prepared meal on hand. We use the orange juice during the course of the holiday, and on the day before we leave buy some in France and ask the site owner to freeze them for us, so we can keep our lovely French food cool on the way home.
We had a really good combinations of cool bag - which would actually keep things frozen for two days - but sadly the outer one got damaged and the replacement is not as good at keeping the temperature down.