When one contemplates that a vast majority of goods imported into the UK from overseas comes in via a container (Clothing, furniture, domestic goods, machine parts, medicine, toys, computers, mobiles and lots, lots more) you begin to understand that shipping container are perfectly designed to be the ultimate storage unit!
Our containers are modified shipping containers and completely waterproof (our insurance covers this) with vents providing continuous air flow. We have had customers storing everything from electrical equipment to furniture and never had an issue.
What we do recommend is that customers try to avoid bringing moisture into the container. Water brought in will evaporate and take some time to escape from the container. With that in mind please ensure freezers are defrosted and washing machines etc are fully drained down.