The fridge part of our fridge freezer has packed up. The freezer part is absolutely fine. Looking at a new one on the Currys website and they will take away the old one when they deliver. They state that fridge freezers must be defrosted first but mine is frost free? Do I still need to switch it off overnight or will an hour or so do? Really don't want to lose all the frozen food in it that's perfectly fine! Thanks in advance!